We had the exact same problem, 10.6.8 fully updated (same problem when it was 10.6.6).
Deleted the printers, set them up again etc. etc.
Created new user.
On other simular computers at the same customer print was not a problem!
Could have erased the disk and installed all over. But I was a bit in a hurry, so instead we updated to Mac OS X 10.7. That solved the problem.
Not the most elegant solution, but ...
Try reading the crash reporter in the Console. That may have a clue for you.
Nice to know that someone else has had the issue, and that none of the usual suspects was the cause!
Don't think OS upgrade is an option so will recommend they erase and re-install!
I had a quick look at the log when it crashed one bit it didn't make much sense to me!
Have you tried sending to different printers? One of our server databases (FMS 11, clients FMP 11, OS 10.6.8) has print scripts that work fine to the clients' networked printers, but crash FM after printing to networked copiers. I suspect that our problem is related to the driver for the copier, and wonder if anyone has seen this.
Pretty sure we tested this, but long time ago now so will double check.
Another update, user upgraded to Lion yesterday -no change!