Other issues I've had to deal with were:
"The printer prints out 99 copies of all our reports from the server, but prints normally when I use it from a local PC".
The printer had been serviced and the engineer set the default number of copies of each page to 99 and didn't put it back afterwards. The software on the local machine set the number of copies to print every time. The software on the server assumed the default was 1 and didn't bother to specify it.
"The reports aren't coming through to the printer. I know it's a problem your end because I can ping the printer and it replies."
Cleaner had unplugged the printer, which wasn't directly connected to the network, but went through a print server. The print server was replying to t he pings.