Sounds to me that you could be having the same problems I had- java memory low problems. Java is extremely memory hungry. I upgraded my computer last week to 4gb memory running Vista 64 bit OS. Go into your Java via the OS control panel and you can increase the Java memory allocation to not more than 75% of your computers RAM. Check out the Java website for instructions- the command is something like Xmx2560M (2560 being 75% of your computers installed RAM.
SO far, touch wood, my PC is running fine and very fast, no more irritating lock ups
