Hmm that's unexpected! I don't know why that should happen.

There are some mac maintenance things you can run thru:
1. SAFE Boot & Repair Permissions

2. Resolving Disk, Permission, and Cache Corruption

If still problems then trash the program folder & re-install. If still problems, try the beta.

Which version of Java are you using by the way; 1.4.2 or 1.5? Did you do anything to the system lately such as updates?