As stated.  Opened a project in X1 that had been done entirely in 8 and it was perfect.  After a week of recording and mixing with X1 I no longer wanted to keep 8.0 around, so I unsintalled it.  After doing that, now all the VST effects I had installed (and they all worked in both 8 and X1) stopped working.  Sonar sees them during the scan, but I get the error warning when opening projects now, and the plug-in names are in parentheses.  (The sonar fx work fine.)  

For the heck of it, I reinstalled sonar 8 PE but then that got the same error message, so I uninstalled it again.  I've uninstalled and re-installed several of the plugins more than once and the result is always the same.  Also, many of the plugins are just .dll files that worked after simply copying them into the vst folder/s.  I'm stumped as to why X1 can't use them anymore.  
Any help is greatly appreciated.  Thank you.

You should not have uninstalled 8.0

Previous version will always happily co-exist with later versions of the software and uninstalling it may well remove stuff in your shared folders - which seems to be the case here.

Which VST's are we talking about?

Did you go into the registry as part of your uninstall to remove the references to 8.0?

If you didn't then any subsequent reinstall won't work 100%

These are the 2 you should remove:

HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\8.0
HKEY_LOCAL_MACHINE\Software\Cakewalk Music Software\SONAR Producer\8.0