mudgel, I did reinstall Dim Pro again, rather than move any files. And thanks for the registry edit option, but I'd prefer to try and find a less technical alternative first if I can - I'd prefer not to touch the registry so soon after purchasing the PC and installing Sonar. Last resort, maybe.
Grum, I already attempted your workaround but since the synths won't load, I can't open Dim Pro to find out which patch it is, so I can't reload the patch.
The actual error message I get when I try to load a project on either the 32- or 64-bit version of X1 says: "The following plugins are referred to by this project but could not be found. They may be missing or improperly installed on your system. Dimension Pro (Synth Rack)."
Grum: "P.S. When I went to 64 bit from 32 bit it junked just about every track with a plugin so if you are just having Dim Pro trouble you are lucky."
I thought I'd remembered some discussions on similar problems myself, but had trouble finding any when I tried a search. Anyway, I anticipated that there'd be some teething problems (I'd already had months of experience with X1!). It seems to work okay with new projects, at least.