Odd. Did you migrate when you installed Platinum?
Can you check in the registry whether the VST bitmap cache path is pointing to the right place for platinum?
(If you don't feel comfortable editing the registry dont do this)
To do that open the registry editor (start | regedit.exe)
If you are running X64 go to the key HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR\Cakewalk VST X64
For 32 bit SONAR go to HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR\Cakewalk VST
Look at the string VSTBitmapCachePath
It should say %APPDATA%\Cakewalk\VSTBitmapCache\SONAR
If not change the value to that and then run SONAR again and rescan your plugins.
See if that fixes it.