Vista - HP Officejet J6480 Sends but won't Receive Faxes IF the COmputer is ON!!

This one is a doozie IMO. I have a new HP Officejet J6480 All in One printer/scanner/fax set up as a wireless network printer. The scanner and printer work fine. I can send Faxes with no problems BUT I can only RECEIVE a fax IF the computers are OFF or SLEEPING!!! If ANY of the network computers are on the fax answers the phone, says connecting (as it should), but then fax intake transmission always fails.

I didn't realize at first because I faxed myself from work and the faxes always went through...then I tried the HP Faxback number just for fun and I got the failure. I tried everything I could think of and sent a dozen faxes to them then when I shut down my computers I got a fax bacK! I tried several times since then and fax reception ALWAYS works with computers off and ALWAYS fails with any computers ON!

I tried shutting off the firewall and reinstalling the software to no avail. I can scan to any computer from the printer/scanner but the fax intake never works if any computers are on. I tried turning off the fax to computer option but it makes no dif. HP no help at all.