Windows XP - SP3.
My Fallout 2 game crashed every time at the temple. I am using Megamod 2.44.
I know I'm really late with this answer and probably shouldn't post here, but I wanted to share my solution to your problem which I also experienced. After uninstalling Megamod 2.44 and Fallout 2 and ALSO completely deleting the folder where they were installed I did these things, in this exact order:
1. Install Fallout 2 from GoG
2. Delete ddraw.dll and ddraw.ini from the Fallout 2 folder
3. Rename patch000.dat to patch000.bak or something similar ( you could also delete it)
4. Install Megamod 2.44
And the problem you described was solved :)
Before doing the stuff on the list above, I also tried updating my Directx9 files but that didn't help at all...
I'm running Windows 7 64bit..
Hope this helps SOMEONE :D