If the DVD plays on a standard DVD player then yes it does appear to
be a Codec and/or protection problem. DVD's are encrypted and unless a
PC has the necessary decryption software then it isn't readable. In
Ubuntu this is a package called libdvdcss2 but you may need to enable
the Medibuntu repositories to get it ( www.medibuntu.org ). Medibuntu
also has the Codecs necessary for playback.

Windows also needs software to play encrypted DVD's which isn't
installed as standard - to get it on Windows usually means buying a
DVD playback program such as WinDVD or PowerDVD but some DVD players
have cut down versions ( missing some of the more advanced functions
but enabling playback of encrypted media ) of these supplied with
them.

As for recording DVD's from your VHS player - again the correct
software is needed but also a video capture card ( standard video
cards don't usually have this functionality ). This applies to both
Windows and Ubuntu.