Hi!

I had the same problem, but ratDVD ran fine some while ago, so I checked what I changed:
To test and watch several format, I installed 2 codec packs and everything was OK, except ratDVD.
I just uninstalled all codec packs and violá, ratDVD works like a charme again

My advice: Check, if you have codec packs installed and uninstall them!

PS: I'd REALLY like to know which codec inteferes with ratDVD, as I need some codecs from the codec packs ...