Which OSX version are you using. If you can, update your version of Java for that OSX version. I know with 10.3 there was a Java update a month ago that was supposed to fix some of these problems. Though if it did it was only marginal.

1.5 GB is not a lot of space to work with! Do you have your HDD partitioned. In OSX all applications use Virtual Memory. Which of course means taking up HDD space. So your game would do that & OSX also needs space. In fact I just checked mine & OSX alone is using 1.1 GB VM.

How much ram do you have?

May I ask how many incomplete & shared files you have? You can round it off if you like. Just an approx but reasonably accurate figure.

Do you ever use the Resume function? If yes, do you do it on many files over the period of a day/session?