[Nogg]

There are instructions somewhere, but here's the quick version:

plug your reader into the usb on your computer
hit the reset and toggle the power switch

at this point it should eventually make it to the usb connected screen

then:
run the firmware installer far enough to have it extract the files and without closing it, copy off the wzse0.tmp or wzse1.tmp folder from your C:\Documents and Settings\<username>\Local Settings\Temp folder

with the wzse0.tmp or wzse1.tmp folder, find the prsversion.dat file, open it in notepad or some other text editor and change the trailing 0 to a 1, then run prs-500Updater.exe and let it reapply the firmware update

That should get you working again