That's probably not GOG related, but something to do with T2X using a different codec for the movies.
Can you play the movies outside of the game? if not, look in the T2X installation folder for the VP3 codec and try reinstalling that. If that doesn't work, you may try ffdshow, make sure it's set up to decode VP3.
If all else fails, renaming the "movies" folder should allow you to play the game (without movies).