I finally finished the game last night, despite certain joys like being locked out of the path I'm supposed to take to proceed, thanks David Perry! I think this would have made a much better console game, rather than a sloppily coded, poorly tested and barely patched PC game. The controls seem much better suited for a controller as well.
Anyway I thought I'd share this little gem after that abysmal 10-second excuse for an ending (and playing on Messiah mode no less). See attached.
The entire credits sequence looked like this, and was accompanied by annoying stuttering audio. Sigh.
(XP Home SP3 if anyone is wondering. The +! command line argument makes no difference for me in any regard.)

Also Just finished and got the same problem, I've the same OS, tried to change my resolution... without success, extremely nice game tough.