DVDSetDVDRoot: Root not set

Hopefully someone will be able to help with this; it's been driving me 
crazy for a couple of weeks now.

I am trying to play a DVD using ogle (ogle-gui) and when I try to "open 
disc", I get the following errors:

libdvdread: Using libdvdcss version 1.2.8 for DVD access
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't seek to block 256
libdvdread: Can't open file VIDEO_TS.IFO.
ERROR[ogle_nav]: faild to read VIDEO_TS.IFO
callbacks.on_opendvd_activate(): DVDSetDVDRoot: Root not set

My DVD drive is /dev/hdc, and I have created a symlink at /dev/dvd.

It doesn't matter whether I mount the drive or not, and if I mount the 
disc and try to directly open the .VOB files, I get the same errors.

Does anyone have an idea?

I'm running Red Hat Enterprise WS version 3, but of course Red Hat doesn't 
support Ogle.

Thanks in advance.

M