Why is Compressor freezing when compressing?

Hi,

I would really appreciate help with this problem. Compressor has recently started freezing / getting stuck when compressing. This happened a couple of years ago and was resolved by using Compressor Repair 1.1.3. I've tried the Repair programme but, on this occasion, the problem is not solved. I'm using Compressor 3.0.5 on a MacBook Pro OSX 10.5.8. When Compressor froze today, I was compressing a 3GB QT movie using the H.264 codec.

I would appreciate any and all advice please.

Many thanks,

Fiona.