I've been clearing the Application Event Log anytime I've addressed a code bug it's reported.
I can still compare the global.asa between the two machines since it hasn't been edited on the old machine, although I'll have to take into account the edits I made this morning. Prior to that, it was the same as was copied from the old machine.
Just checked. Identical. I don't know if global.asa is ever read beyond IIS startup, though. It's possible that the changes I made to it this morning had no effect until the reboot.
The line in the global.asa that was trying to store too large a number as an integer shouldn't have become a problem until 2 days ago when account numbers first exceeded what an int could store.
I'm going to go through that link you sent me and check on everything it says to check and get things ready to make the suggesting testing go as quickly as possible after the next crash. The next time it happens, it might be down for a bit while I try those suggestions, but I'll limit my testing time to no more than 5 minutes.