I upgraded my RAM to 48 GIGs to support some specific application needs. Consequently I needed to begin booting my 2009 Mac Pro in 64 bit. I've been using it this way for about a week and most of the time it is great: seemingly brisker, and the additional RAM is great. But....But at least six times total and twice tonight I've had nasty freezes where the finder will get hung up and will not be relaunch after a force quit. A hard re-boot will be my only option. I never have seen this behavior before so naturally I attribute it to booting in 64 bit. I've looked at my Activity Monitor and scanned for culprits...I've removed or updated several borderline preferences/bg apps, and as many 3rd party 32-bit resources as possible. I've done the obligatory repair permissions. Any suggestions on what can I do next?