"Failed to open a session on the device"

So I have a HP Officejet 6500 Wireless all-in-one, and up till about a week ago, the scanner was working normally; I would go into Print & Fax preferences, click on the printer, then the Scan tab, then "Open Scanner". It would open up the scanner window, say "Connecting to scanner" or something like that, and then give me an overview and all the options. Now, however, whenever I open up the scanner window, it says "Trying to open scanner session..." and then "Failed to open a session on the device". I've restarted the printer, my computer, tried to open the scanner window from Preview, even deleted the printer and re-added it. But it still gives me "Failed to open a session on the device".

Connecting to the printer with USB does the exact same thing.

Thanks.