VSTs not being scanned after upgrade

[sethman]

I just downloaded and upgraded Reaper to v6.03 and now the vast majority of my VSTs are no longer available. To troubleshoot I've:
-rescanned
-cleared cache and rescanned
-deleted and re-added my folders to the VST paths
-created new folders, moved my VSTs to them, and added those folders to the directory path

Nothing seems to allow roughly 70% of my existing VSTs to be re-discovered. What can I do to get them back?