HP Deskjet 1050A doesn't scan, only prints after reset



I work with a Deskjet 1050A (J410h) and a MacBook Pro running Mac OS X 10.8.2. Recently, the scanner stopped working: when I try to open the scanner via System Preferences -> Print & Scan, Image Capture or Preview, no overview is generated, and all the buttons are greyed (screenshot 1); when I try scanning via HP Scan, I'm informed that an error has occured, and that the computer has "failed to open a session on the device" (screenshot 2).
Possible solutions that didn't work: rebooting the computer, rebooting the printer, resetting the printing system, removing the device then resetting the printing system, hoping really hard that the problem would magically fix itself. Any other ideas?

Another, possibly related problem: often, when I send a job to the printer, the computer starts "waiting for printer to become available" (screenshot 3), and will only print after I've reset the printer (by unplugging and replugging its power cord). Any thoughts?

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