When in IFO mode, click on the Stream Processing tab, then tick it on. You can now tick the video & audio streams you want to extract (still in VOB file format). The final set of vob files etc cant be played by double clicking any IFO file as per ususal, but each individual VOB file can be played to check all is well. I use WinDVD 5 as my player.
Then in Vidomi, what are you selctiong? Are you using DivX or Xvid and what versions of the Codec of each have you installed?