Have you have you tried restarting the system and renaming the file/folder? Then after doing so deleting it?

What type of DVD are you attempting to convert and is this occurring on more then one disc? Also what version number of the program are you using?

If you are converting to Mp4 try using a different media player such as Itunes or Quicktime to playback the file.

I'm sorry but the information we need above was whether you were using the Entire disc to single or dual layer disc option. Also how large is any of the DVDs your attempting to copying?

At install are you installing all the components available such as Avisyth , Microsoft C++ and the Dot Net framework shown in the install list ?