clicking intro does not crash the game, however it doesn't do anything at all

i have the k-lite codec pack installed

Running THIEF.EXE with Administrator privilege fixes the movie problem for me, and I have K-Lite Codec Pack installed as well.

I am able to utilize DDFix and the Dark Engine Resolution Patch using the GamersGate version (v1.33) of THIEF.EXE from Thief: The Dark Project (not Gold) with the GOG release, and it appears to work great.

DERP is an important piece of restoring the modern Thief experience. Hopefully GOG will update their release with a compatible EXE.

I was also having issues where when the mission was about to start, the application would crash with the generic Windows application has crashed message. Strangely, I had been able to play the training mission twice earlier, but now even that crashed.

I rebooted, and the game seems to run fine now.

well would you look at that, a reboot worked for me too!