I don't have proof, but here's what happened:
I got 64 bit Reaper. Installed, started downloading all my free plugins that I always use. Messed around on a quick "dummy" session, and for some reason I opened ReaPitch. This plugin would cause Reaper to crash every time I used it.
ReaEQ also had a bug where the little graphic analyzer was missing and none of the bands could be altered. I know there were a few others, but I can't recall now. But that was enough to make me not want to use it.
I did try uninstalling and reinstalling that version with no luck. Then my HDD failed when it was only 1.5 months old. Got a new one along with an SSD. Installed 64 Reaper again. Same exact bugs happened. Ditched it and went 32 bit and never looked back.
I've also heard other guys on this forum ran 64 and never had problems. *shrug*