For awhile now I've had a problem with Vegas randomly freezing when rendering with the GPU, a problem that goes away when I switch to the CPU (sorry, but I can't find the other post I made on this topic). I think I've found the culprit.

When I go to Properties and set "Deinterlace method" to anything other than "Smart Adaptive (GPU only)", then it works perfectly. The thing is, I still have the problem with Smart Adaptive deinterlacing even when none of my media is interlaced!

Anyway, hope this revelation can make headway towards fixing the problem!