audio out of sync

Captured some footage from DV camera into Ulead Media Studio Pro 7; edited it and got mpeg that worked just fine; imported into Ulead DVD Workshop 2, chopped it into chapters, added menus and previewed the whole project - still all worked fine; got to the stage of converting the project to DVD files - regardless of what template I chose (high quality, standard quality, 60 min per DVD etc.) the "required disc space" tab showed the same value - peculiar; nevertheless, proceeded with creation of DVD files and ended up with a project where audio is out of sync (the first 40 minutes are fine, but the rest 60 min. have audio about 1 sec. before video). Tried various templates, but always ended up with the same result. Furthermore, file sizes were identical regardless of the template I used. Tried defragmenting the drive - same thing.
Thaught it was a DVD Workshop issue, so authered DVD with DVDLab. Same thing and it's really driving me nuts!
It shouldn't be a hardware issue, cause I authored few DVDs without any problems before formatting the drive a couple of weeks ago. After formatting I installed XP + SP2 (before I only had XP). Could it be the driver issue and icompatibility with SP2? What hardware drivers should I concentrate on? If not, what else could it Be? Any ideas?