After installing Bonjour for Windows you will notice that when you reboot the Printer will be offline.
I have seen many explain the hard way to fix this when using Windows XP.
Here is the short way.
With the printer selected as OFFLINE.
Goto Maintenence tab in the selected printers PRINTER PREFERENCES
Click AUTO POWER, and change the it to Auto Power ON
You will now see that it is trying to send a request.
Open the PRINTER STATUS MONITOR
and you will find that the USE PRINTER OFFLINE is checked.
You should now find that the printer has come online after it has pushed the request thru...
Hope this has fixed your problem