Beyond Pictures Blog: VOB Files and Adobe Premiere - Editing from DVD has two methods to work around this issue - rerendering in virtualdub or frameserving to Premiere from AVISynth.

I would strongly recommend you learn how to use VDub and AVISynth, they are incredibly powerful and free tools.

Also see VirtualDub-MPEG2 for an mpeg2 version of virtualdub which may help.