My Mac sounds similar to yours except I have more memory, using 10.6.8 and only periodically use PS6. (I'm mainly an LR user these days, unless I need something it doesn't have). I think when you have this kind of problem, it could be that something in the OS is interfering with the expected operation of certain applications. I suggest you may wish to do a system check with the Mac Disk Utility (Applications>Utilities>Disk Utility) and see whether it turns up the need to repair or trash any permissions or preference files, and repair as indicated. The other popular way of doing this is to download a copy of Drive Genius 3 and use that. (But stick to one or the other.)