Just opened an old X2 project I'm going to update and...up jumped the devil.  First their are several tracks that won't play at all and they are also behaving in a strange way.  For instance when I try and solo a track in Kontakt...it also solos the Stylus RMX track.  If I try to open Kontakt I get the Stylus RMX gui instead.  I was able to insert new instruments and copy the midi into them and they will play so I can probably recreate the track.  Hopefully.
 
The other problem is that there is no synth rack icon or way that I can find to make it appear so I can delete the older now unused synths.  There's no little arrow on the right side to expand the browser or anything.  It's like the project is opened in X3 but running like it's still in X2.  Weird. 
 
Your thoughts?

So, you hit 'B' and the browser does not appear?  Or, the Browser is there but you cannot get to the Synth Rack?
 
Also, if your midi data was preserved, I am a little confused as to your comment about having to 'recreate the tracks'.  Are you referring to effects and such?
 
Are you opening these old X2 projects in X3?  Do you still have X2 installed?  Have you tried opening them back in X2?
 
I am just trying to better understand the situation - thanks for putting up with the questions.
 
Bob Bone
 

Were these old projects created in a 32-bit Sonar X2?
 
Just curious, 
 
Bob Bone
 
 

Can only offer limited help for this. Is it possible the DAW uses multiple monitors. If so, I have read of instances where floating windows go off screen on the second monitor. The keyboard shortcut "B" probably won't help because it will open the browser at the last location which may not be visible. The Browser may still be attached on another screenset providing access to the synth rack while trying to figure out where the floating browser has gone.

These were done in 64bit X2. And as I said, yes I can apparently insert new synths, copy midi to them and get them working again. I just meant that I'd only done that to a couple of tracks and HOPEFULLY the rest would be the same. I think I tried B but will again when back at the studio tomorrow. I even tried shutting off all effects...then deleting them altogether to see if they could be causing the certain tracks not to play. No love. The tracks that aren't playing are some from Kontakt, a Wavestation synth, EZDrummer, and Lounge Lizard EP3 track. My Stylus track and all my Omnisphere tracks all play fine. I'll just "re instrument" everything and start back at square one.

The thing that concerns me most is that this is the first of several X2 projects I need to update and finish. I hope this won't be how I have to deal with all of them.

Sooooooo, do you still have X2 installed on your computer?
 
And, did you do BOTH a reset AND a FULL re-scan of your plugins?
 
Bob Bone
 

Yes and yes.

Did you install X2 after X3?
Will it open in X2? (Backup first)

One more thought about the missing browser, temporarily reducing screen resolution should bring off screen windows back into view.

As far as synth playback goes...  have you by chance installed EZ Drummer 2 since the project was last opened?