Some information that might be helpful from the error report that windows gave:
AppName: dwarfort.exe ModName dwarfort.exe
Offset: 0001eee2
Exception Information
Code: 0xc0000005
Flags: 0x00000000
Record: all 0s
Address: 0x041eee2
The stupid error report doesn't let me copy and paste, so I had to retype that. It just wants to send it to microsoft. I let it send, though I doubt they'll know who to send it all to.
I haven't modded the game's files, I don't think.
It crashed twice in a row (after loading), but after I did things - I tried loading a third time and not doing anything, and it didn't crash, so it's something I'm doing. I'll see if I can figure out what. Perhaps ordering the building of walls on ramps, as that was the last thing I was doing before it crashed each time.
Edit: It just did it again while I was changing z-levels, for no obvious reason. Maybe I wasn't waiting long enough after loading the saved game, or maybe it was a time-delay after pulling the lever that I just pulled a minute ago.
Edit #2: Bingo! I now have a saved-game which crashes about 10-20 seconds after loading and unpausing - A dwarf runs over, pulls a lever, a hatch closes off-screen, and then a few seconds later the game explodes like Alderaan. Saved game: http://shadowlord13.googlepages.com/crash-10-20sec-after-load.7z
P.S. The hatch in question is providing access to the magma vent for the feed tile of a bauxite pump, and magma output from said pump also flows back around to that same tile and can fall back down there.
Edit again: Movie which shows the pump and stuff which the hatch is the input feed controller for (It's for the pump which feeds from the magma vent): http://www.bay12games.com/cgi-local/ultimatebb.cgi?ubb=get_topic&f=6&t=002749
If you want to look at it in-game, you can prevent the crash by cancelling the lever-pulling. The lever is off to the west down a hall a bit.
[ February 04, 2008: Message edited by: Shadowlord ]
[ February 04, 2008: Message edited by: Shadowlord ]