WHAT IS UP WITH DISAPPEARING PLUGINS?

Yesterday, X3 only showed about half of my plugins in my "Vox" folder (part of a custom layout), leaving out several, including Melodyne, which was there a week ago.  Now they're all gone from the same folder except for Cakewalk Pitch Shifter!!!  Some other plugs are missing as well from their folders.  I have changed nothing since a week ago.  No updates to any software, including X3 (X3b) or Windows.
 
Weirdest part is when I go to manage my plugins, they are all there; I then go to insert one in an audio track, check that the proper layout is selected, and all of the folders are there (i.e., vox, compressors, modulation), but many of the plugs aren't showing up as available to insert. 
 
They are all VST (not VST3).  I even tried "default all plugins" and no Melodyne and other plugs.  So I gave up, opened up X2, and same thing!
 
I scanned, re-scanned, and reset all plugins, waited for the interminable initial scan and...  same thing.  Re-started Sonar, restarted PC...
 
Anyone else having similar issues?
 
Also, what's up with the new scan (I forget what they call it)?  Sure, bottom right corner and you can close it, but X3 is totally sluggish until it's done.
 
What am I doing wrong - or what is Sonar doing wrong?  Again, it all worked a week ago, so far as I could tell (possible I didn't examine plugs too closely).