That would be why the calculator won't work- it probably is designed for a lower version of firmware.
So far there haven't been many demos released other than the ones that came out with the firmware upgrades. I did find one more that was leaked from the Tokyo Game Show, it's for a kart racer of sorts based on Ape Escape (you knew it was just a matter of time). If you'd like to give that a try I can e-mail it to you along with instructions on which folder to put it in.
There is a PSP demo disc with the November issue of the Official US PlayStation magazine- it's a demo of Killzone: Liberation, I believe.