Jobs hanging; have to shutdown and restart printer.. (in imanage)

Basically that says it all.. running Nw6.0 w/ sp4

Happens usually at least once a day (we have around 150 networked
printers).. As soon as you shutdown and restart the jobs start
printing; you don't have to do anything to the physical printer..

If you look in Web JetAdmin and look at the printer; everything is fine..

Seems to be a server related issue; not a workstation issue since the
print jobs that have "hung" the queue have been from 9x to 2000
workstations with different versions of the iPrint client..

Anybody run into this or have any suggestions??