Good to know, thanks. 
Right now on both my DAW computers Sonar opens with in seconds. 
Most projects also open fast but they always seem to have trouble making up their mind about the "lens" and flash about with about 3 or 4 different views before settling down. 

I use the default scan settings which include automatic background scan. Never had a problem using it.
It seems strange the Plug-in Manager takes so long to start up. All it is doing is reading the registry and populating the different plug-in types. There is no scan going on when starting the Plug-in Manager. This may indicate a problem with the registry. A VST reset will rebuild the the VST Inventory portion of the registry but if the problem is the with the DX entries it may be harder to repair.
 
If you believe it is related to a particular version of SONAR, roll back to a version prior to experiencing the problem. If the problem goes away it may be related to the newer release. If the problem does not go away, it is likely not related to the newer release.
 
WRT slow scanning here are some tips.
 
Make sure the scan options "Rescan Failed Plug-ins" and "Rescan Existing Plug-ins" are not checked. These are used very rarely to fix certain problems.
 
Double-check the scan path. If you are unsure about what to look for in the scan path post it here. The scan path should contain paths to VST plug-ins and not have multiple references to the same folders. For example if there is an entry in the scan path "C:\Program Files\Cakewalk\Vstplugins" there should be no folders under it in the scan path such as "C:\Program Files\Cakewalk\Vstplugins\Rapture." Having redundant paths are a problem.
 
Use Preferences > File > VST settings for scanning operations. Reserve the Plug-in Manager for handling plug-in exclusions, layout maintenance and preset import/export.