Which mac os do you have? If you're using OS9 make sure you have the most recent version of java for os9. Likewise for osx. It sounds like you need to check your computer (OSX repair permissions & do a safe boot.) For os9, rebuild your desktop & defragment your hdd. Also check your disks over with a file/disk utility such as norton/DiskWarrior/TechTool Pro, etc. A corrupted directory can cause major issues when trying to do anything.