Always good advice for any computer owner.
Another possibility is a conflict with other software you may have installed...and that is going to be hard to isolate.
Especially suspect are any program 'add-ons' that you may have loaded for un-related (un-related to DVDFab, that is) software. 3rd party authors rarely pay attention to the finer points of software inter-action, and as a result, these add-ons can cause problems across your system (such as the freeze situation your have with Fab).
Something else to check.