my printer (HP8500) is wi-fi connected to my imac and my macbook. works fine from macbook, but has stopped working on the imac--shows offline. How can I fix this? Thanks

I have an iMac and MacBook Pro, both running Snow Leopard at current maintenance levels. I have an HP8500 printer connected via wi-fi. All have been working well until just recently. Now, the iMac cannot communicate with the printer. The printer icon shows offline. The printer is still online to the MacBook. I suspect a related problem is that when I try to access files on the MacBook from the iMac, I get a message that they are unavailable, but re-clicking once or twice to re-try works and the files are accessible. The only problem is that I cannot modify them from the iMac, even though the sharing options are set for update capability.

Resetting the printer and re-booting the iMac don't help.