Print 3 times then reboot

I have a customer with NT4 Back Office Server (they are running Exchange) and ?9x workstations. Users occasionally must reboot to continue printing particularly from Outlook. The problem is inconsistent. I have tried a print server but this did not solve the problem. The C partition in a RAID5 array is down to less than 10% but plenty of room on the other partition. Event view shows numerous cases of zero case size and zero pages printed. I will try anything reasonable, I am almost out of hair to pull.