thanks for pointing me to that software - I've never heard of it before.

You can solve the problem by, when playing a VIDEO_TS folder via DVD 
Player / DVD Assist, keeping the menu button pressed, enter the menu 
and activate the DVD Player behaviour. To then return to Front Row, 
press the menu button and deactivate the DVD Player behaviour.

Considering DVD Assist is a hack and Front Row does have its own set 
of problems (i.e. by starting iTunes in the background) which require 
Remote Buddy to handle it with special care to be reliable, direct 
support for DVD Assist is unlikely, though.

Best regards, 
Felix