Help!

We have a very strange network printer problem and for the life of me I can't think were to go next for an answer. When we come in of a morning the client machines are showing their network printers as offline. However - all network connections check out, everything pings, DNS is fine, print server is running, print server sees the printers as online and prints test pages.

Come about 8:15 the client machines suddenly show the printers as online and everything is fine for the rest of the day.

Anyone have any ideas what is going on?

Thanks