While I may not get my money back by doing this, I have found a very simple solution to all my not-being-able-to-play-Thief 3 problems. All you have to do is go to www.gametap.com
and sign up for a totally free (unless you want to start a subscription to gain access to other games, but that's pointless for just Thief) account. Then, download the launcher, and download Thief off of this Gametap program. Now, for those of you unfamiliar with Gametap, it is ONE HUNDRED PERCENT legal! Thief just happens to be one of the games you don't have to pay to play on Gametap. If you're frustrated with Steam like I was (CURSE IT!!!!) about not letting you play Thief 3, or you have some other problem that might not even be Steam-related, try just this one more thing. Get Gametap, which takes about 5 minutes at 90 K/B per second. Unlike Steam's version of TDS, which is 2 gigs, Gametap's is only 800 megs to download. Gametap worked like a charm, and I'm making my way through to the Cradle as we speak! I can hardly wait to be scared (bleep)less by the undead mental patients. For anyone else having really annoying problems with TDS, try this, please! Give this game one more chance.
(And yes, I realized I've posted this in my old thread, but I want to make a thread simply dedicated to this. Also, I think someone on the forums might have already discovered this, but I don't feel like finding it if it exists and bringing it back from the dead)
Post a reply if this worked for you.