From the PC's perspective, the printer must be offline, no other choice available to it (the PC) to make about the printer's current state of mind. The printer isn't answering there at the other end of its USB port, which is how was told (when you installed the driver) it should be able to communicate with this particular printer.
Now, how did we get there? You unplugged the cable. Yes, I know you plugged the cable back into the MAC, but the PC doesn't know that. So what do we do next? That's the head scratcher, for me anyway.
Typically in a complete PC environment, the printer is connected to its usual host in the conventional manner. Another PC on the network wishes to use that printer. You go to the Add Printer wizard, tell the wizard you want to use a printer that is connected to another computer on the network, the wizard looks up and down the network to find all the printers that other computers have, and asks you which one you had in mind (and often there is only one other one). You say "yeah, that one", and the wizard then does what it needs to find an appropriated device driver and link to the networked printer.
In a mixed Mac/PC environment, I don't know right off hand what will happen during the "the wizard looks up and down the network to find all the printers" phase that I just described. Will Windows ask the right questions of the Mac? Will the Mac give the right answers back to the Windows? That I don't know because I haven't tried it, but I do think that is why your setup isn't behaving as you want it to.
dw