Subtitles in GMPlayer

Hi,
When I rip a DVD-chapter to an .avi file, generating the .sub, .idx, and 
.ifo file, I'm not able to play the movie in none of the installed 
players (xine, GMPlayer). In GMPlayer the subtitle menu is shown only if 
I specify the -sub switch on the commandline. In that case subtitles are 
available. Otherwise the subtitle menu is hidden. In xine I can select 
the subtitle menu and select subtitle 0, but it is not shown.
Please can anyone help me to show the subtitles on the movie (without 
baking them on the avi-track).
Is this a specific MPlayer problem or do I need to change settings in dvdrip
I have a straight forward ubuntu 10.4 linux box.
Thankx
insomniux