After constant complaints from one client, I found this fix by Phil martin.
Apparently, the problem is caused by HP driver on Vista. The wireless connection to the printer would just drop and indicating that its offline. I had been to the job site a couple of times just to merely turn it Online.
Fix: Disable the "HP CUE DeviceDiscovery Service".
Steps:
1. Start -> type in "services.msc" and Continue/allow to the services window.
2. Look on the right panel for "HP CUE DeviceDiscovery Service" and double click on it.
3. Click the STOP button.
4. In the Start Type option, select Disabled and click on Apply button, then OK.
Note there's also an update patch download at the HP download page http://h10025.www1.hp.com/ewfrf/wc/softwareDownloadIndex?softwareitem=oj-67880-1&lc=en&dlc=en&cc=us&lang=en&os=2093&product=3204785
Since the HP Cue disabling might not work, as in my case.