I'm running X3b Producer 64bit on a Win7 x64 system with 400+ plugins. Every time the plugin manager scans the plugins, it duly scans through all of them apparently without difficulty (I removed all problem plugins that had returned error messages), duly reports that it has rebuilt the menus, and then invariably I get a popup crash report -- a Windows message stating that Cakewalk VST Scan has stopped working.  When I close out the popup crash report and return to the plugin manager, the plugins do appear in the registered plugin window, so they appear to have been scanned. But back in X3, the insert soft synths drop down menu includes only some the registered plugins and omits others without any apparent rhyme or reason (for example, Fabfilter One is there but not Fabfilter Twin). Using the plugin manager, I can create a custom menu that includes all the registered plugins, but they still do not appear in the insert soft synths menu when I select the custom menu there. They do all appear in the custom menu when I select it in the browser, but only the plugins that also happen to appear in the insert soft synths menu (e.g. FabFilter One but not Fabfilter Twin) can be loaded as new instrument tracks by double clicking on the plugin name. The other plugins can be loaded only by clicking on the plugin name dragging it on top of an existing instrument track to replace a previously loaded instrument -- double clicking on the plugin name in the browser does nothing.  All of this has been extremely frustrating.  I have tried rescanning the plugins multiple times (sometimes with only a small number of core plugins just to see if it would work), rebooting multiple times, even uninstalling and reinstalling X3, but I still get the same crash report every time and the same dysfunctional behavior in the insert soft synth menu and the plugin browser. Can anyone help diagnose and solve the problem? Many thanks in advance.

Stuff like this is hard to diagnose in a forum so I suggest calling tech support and someone can walk through diagnosis steps with you.
If the scanner is crashing, some plugin is causing data corruption and causing it to terminate. So until the scan finishes properly all your plugins won't be available. In another thread there were instructions posted on how to start with the minimum set of plugins and keep adding in plugins until you find the errant one.
You use the term "plugin manager scans the plugins". Are you starting the scan from Plugin manager? It is not recommended to do so in X3, because scanning is handled in the background by SONAR by default. Once it finishes you should see all available plugins in the plugin browser in SONAR as long as you are showing the All Plugins layout. 

Hello,
I can confirm the fact that once you reach around 450+ plugins after a scan then plugins start disappearing from the menu, in a rather random fashion.
 
I use the standard background scan all plugins view, no crashes or error messages appear ... only the plugins disappearing.
 
I upgraded from Music Creator 6 to X3.
In music creator 6 you got a message when to much items where in the plugin view, then you could create a number of custom views and actually access & use the plugins.
 
Now when you create the custom views the plugins are accessible from the custom views, but the ones that 'disappear' from the all plugins views, do not work anymore.
 
I spent hours trying to figure it out, but I think this might be a software bug.
 
 
 

clif321
I'm running X3b Producer 64bit on a Win7 x64 system with 400+ plugins. Every time the plugin manager scans the plugins, it duly scans through all of them apparently without difficulty (I removed all problem plugins that had returned error messages), duly reports that it has rebuilt the menus, and then invariably I get a popup crash report -- a Windows message stating that Cakewalk VST Scan has stopped working.  When I close out the popup crash report and return to the plugin manager, the plugins do appear in the registered plugin window, so they appear to have been scanned. But back in X3, the insert soft synths drop down menu includes only some the registered plugins and omits others without any apparent rhyme or reason (for example, Fabfilter One is there but not Fabfilter Twin). Using the plugin manager, I can create a custom menu that includes all the registered plugins, but they still do not appear in the insert soft synths menu when I select the custom menu there. They do all appear in the custom menu when I select it in the browser, but only the plugins that also happen to appear in the insert soft synths menu (e.g. FabFilter One but not Fabfilter Twin) can be loaded as new instrument tracks by double clicking on the plugin name. The other plugins can be loaded only by clicking on the plugin name dragging it on top of an existing instrument track to replace a previously loaded instrument -- double clicking on the plugin name in the browser does nothing.  All of this has been extremely frustrating.  I have tried rescanning the plugins multiple times (sometimes with only a small number of core plugins just to see if it would work), rebooting multiple times, even uninstalling and reinstalling X3, but I still get the same crash report every time and the same dysfunctional behavior in the insert soft synth menu and the plugin browser. Can anyone help diagnose and solve the problem? Many thanks in advance.

Definitely give tech support a call.  Those guys will be able to talk you through getting this solved. Here are the details for this:
http://www.cakewalk.com/Support/contact/default.aspx#contact-info

Many thanks to all of you for your help.  I followed the advice to use the background scan and that solved the otherwise still unexplained the crash issue -- I just started over, adding plugs/synths to a new scan directory a few at a time and letting CW find them automatically as they were added.  By this method I was able to populate the plug/synth menus without any crash reports from the scan program.  But now I have definitely gotten to a point where Sonar seems to be imposing a limit on the total number of plugs/synths even though it is not supposed to be doing so with this version.  Like noorder.licht, I find that when I try to add to the number of new plugs/synths beyond a certain number (not sure exactly what it is, but somewhere around 500 plugs/synths total), the program will start dropping the bottom ones off the default "All plugins" menu even though they still appear in the plugin manager inventory (zplane's vielklang2 has been a particular victim of this).  So the program still seems to be enforcing some kind of limit on the number of plugs/synths in a menu (and if a synth is dropped from the "All plugins menu" it will also no longer load properly from a custom menu, as I mentioned above). I read in another thread that perhaps this behavior is attributable to bug that will be fixed in the next maintenance update.  I hope so -- and thanks CW for continuing to pursue this issue.

I normally have around 450 plugins loaded but have many more on my system from testing and experimenting over the years that are not normally scanned. In an attempt to beat "bapu" in his record of 1250 or so plugins scanned and available I scanned all the plugins on my system. The result:

I have available in excess of 1000 plugins thanks to the various improvements to Sonars VST scanner. There is clearly something else going on in your systems that is causing this problem. As suggested by both Noël and Dan, contact tech support.

There's another thread where it was mentioned that there is still a limitation specifically for 255 synths vs FX plugins which are now unlimited (was around 700).  Apparently most have a high number of FX vs. synths!
 

Yes I've fixed the issue with the 255 synth limitation for the next update. If you are seeing normal audio plugins go missing however, let me know since that shouldn't be happening. I have over 1000 audio plugins definitely showing up with no trouble. You can verify this by counting the plugins in the plugin browser under the synth category using the all plugins layout. If you have 255 in there then the excess will start to drop.
 

As far as I can tell on my system there is no problem with audio effect plugins dropping from menus.  It only seems to happen with synth plugins over a certain number as you indicate, so the upcoming update should resolve it.  Thanks.