Uninstall as 2:43AM said, but when you reinstall Dim Pro, use the version that comes with S2. It's a seperate installer (also a seperate download) and it will install 1.5 in one go without the need to manually update it.
About 32 and 64 bit plugins: if possible (which it often is) I disable the installing of 32 bit plugins but because some plugins don't let you do that (for some odd reason) I always have TWO Vstplugins folders, one called
Vstplugins 32 and one called
Vstplugins 64. Don't think I need to explain which plugins go where...

Since I use Windows 7 64 bit I only added the 64 bit folder to S2: Sonar doesn't even know that 32 bit folder exists.
It's VERY important to keep those two versions separate!!! Some developers may give different names to the 32 and 64 bit versions but most don't. Maybe 32 bit versions of Dim Pro ended up in your S1 Vstplugins together with 64 bit versions and maybe that's why you see plugins that won't work.
Doing it like this I always know where any 32 bit plugin is going (avoiding a mess on my PC with plugins everywhere) and I always know Sonar won't see them.