the problem is probably not the software but the user permission on your disks and the relationship between Qmaster and your OS.
I had HUGE trouble a while back with compressor and my old G5. There is a lot of information on the net regarding it. I did several reinstalls of all my software, The problem was eventually sorted by creating new users account and operating everything under that new account.
I can’t say if this will fix your problem, But there was quite a problem with compressor in the past for many people.