This is after a clean reinstall of all my apps. Is there a way to make Sonar recognize the plugins in each project as 64-bit again? I know the labels on the tracks and in the synth rack say x64 next to the plugin name, but when I open the plugin's property page, it thinks the panel is "x86". How do I fix this? It's driving me crazy!

Not sure if this will help, but what I do is I don't install the 32 bit plug ins using custom install. It's been a long time since I installed 8.5 but I'm pretty sure it had that option. 
I then install any 3rd party plug ins that are only 32 bit. 
Most 3rd party installs give you options to choose 32/ 64 and other formats. 
You say you just did a re build so might be a good time to try this before you get in there to deep. 

sock monkey
Not sure if this will help, but what I do is I don't install the 32 bit plug ins using custom install. It's been a long time since I installed 8.5 but I'm pretty sure it had that option. 
I then install any 3rd party plug ins that are only 32 bit. 
Most 3rd party installs give you options to choose 32/ 64 and other formats. 
You say you just did a re build so might be a good time to try this before you get in there to deep. 

My machine is 64 Bit, and so is my installation of Sonar.