I'v been struggling with this error for 2 days. mplayer gives me:

Playing DVD title 1
Reading disc structure, please wait......
libdvdread: Can't seek to block 256
libdvdread: Can't open file VIDEO_TS.IFO.
Can't open VMG info!

In ogle I get:
Debug[ogle_nav]: Opening DVD at "/dev/dvd"
libdvdread: Using libdvdcss version 1.2.2 for DVD access
libdvdread: Can't seek to block 256
libdvdread: Can't open file VIDEO_TS.IFO.
vm: faild to read VIDEO_TS.IFO

Can someone kind soul please tell me how to fix what's wrong. In pulling my hair out over this!

Did you install libdvdread prior installing Mplayer? If so, you should remove it and recompile Mplayer, Mplayer provides its own libdvdread which is by far better solution than libdvdread from http://www.dtek.chalmers.se/groups/dvd/downloads.shtml - ogle. and ogle should be fine with it as well.

Thanks so much!
That fixed everything right up. I now have mplayer and ogle working great.