Plug-in Stand-in again.

Have you made sure your 32 bit plug in folder is being scanned ?
Have you tried to load those same 32 bit plug ins and they work fine ?
 
This might be a little out of my league as I haven't heard of this issue before.
Sounds like a mini nightmare though. Sorry for your troubles Bitman.
Been so long since I used a 32 bit system and plug ins for that matter. I use almost exclusively VST3 now.

Hi Bitman,
 
I'm not sure that I would call it a Plug-in Stand-in (don't know what it's actually called) - Sonar has found more than one match for the plugin in question and is asking which to use.  I do agree that they could do better job of giving you specs on what your options are.
 
I've run into the same thing and for me the best fix has been eliminating dupes from my scan folders.
Foe example:
If your only DAW is Sonar the best approach is to not install components you don't need - so if you're using Sonar X64 only install VST3s if availble, if not only then only 64 version.
If you think you might need an old version archive it outside the VST scan paths and if you later find you do need it then restore it.
Sometime the newer 64 bit version doesn't pick up the patch settings of the old 32 bit version - there's been a couple of times where I had to load the old version to get the patch name so I could then replace it with the 64 bit version and manually reload the correct patch.

If you use multiple DAWs where do need to have the VST 32bit versions or nonVST3 versions then organize your VST folders.
For example my VST2 32 bit folders are:
C:\Audio\VST\32 bit
C:\Audio\VST\32 bit (has 64 bit version)
only the top folder is in my Sonar VST scan path, for another DAW that only supports 32bit plugs both would be.
 
This for most part is what works for me, YMMV.
 
Best regards,
...Steven