Aperture and iTunes freezing, bringing down Snow Leopard entirely
Since more than one application is having issues, it's unlikely to be two bugs and more likely to be a system or hardware issue.

Before spending a lot of time, make a new user and see if that user has issues as well. You could have bad luck and lots of corruption in your user folder and this will let you know if the problem is with the apps/system/hardware or not.

Drive Genius might help to run more involved tests, but it might be cheaper to just buy a spare external drive and back things up. You can zero the drive and clear all bad blocks - give that hardware the best chance to work again. You will know soon after restoring your data on the newly erased and installed mac if the problem is resolved.

Good Luck!