Some plugins (many actually) won't work on 64bit, although there are supposedly some workarounds for some.
Some isn't always good enough, though.
I suggest you either go back to 32bit or create a dual-boot system.
As much as I like new/modern stuff, I don't like being too much of a guinea pig. I'm staying away from 64bit for now - at least until it becomes more of a standard.
When upgrading to Sonar prod. 7 64bit, the cakewalk DSP-FX plugins cannot be install because it only runs in 32bits. I have gone to Hell and back, did all the tricks and recommendations but still no resolution. I have projects that required these plugins.
Any help would greatly appreciated.