I don't believe this is referring to software it is referring to the shipping lock on the scanner...the actual lock.

Verify that the shipping lock on the scanner is in the unlocked (open padlock) position
the shipping lock is on the underside of the scanner.
If you have already unlocked the scanner, unplug the power and toggle the lock switch firmly 4 times, then plug the scanner power back in. Even though you may have already unlocked it, the hardware may not have fully disengaged the lock.
Does Visioneer have a drop dead date after which you must buy new hardware?
No, but it may require new drivers...as most scanners do from time to time. This could go for the other one also. When you plugged this second one into the computer did you install all the needed software and drivers? Usually each scanner comes with it's own software and drivers and they are not interchangeable. Go to the Visioneer website and see if there are new drivers available. I know with my Epson I probably have installed at the very least two updated drivers since I purchased it.