I recently bought goty ed. to play on my 360. It did update (huge one at that). But after title and main menu it gives me dirty or damaged disc error. Do i need to get another copy? Or is there any other reason the game won't play? Thanks!

If your Xbox installed the patch (which sounds like you did that) everything should work normally.

Seems like your disc might be damaged. Try cleaning and/or refurbishing the CD. Most video game stores refurbish for around $5

See if http://www.gamesas.com/topic/30-freezing-dirty-disk-error-morrowind-goty/ helps.