Slow Network printing

My info:
Domain, multiple users, network printers installed on server and shared,
users connect to printers. Updated network card drivers on local machine.
Ping, tracert reply no problems.
For some reason out of the blue printing becomes extremely slow for multiple
random users, to different printers. EX. If they hit the print button on a
word document it takes 15 to 20 seconds for a dialog box to come up, then
hitting the print button it takes an additional 20 seconds for it to print. I
did find that deleting the printer object on the local machine and then
reconnecting fixes it but I am wondering what is causing this reoccuring
problem. Any ideas?