I was having an issue with a PIX501 (4.2 Embedded Firmware) just hanging randomly after variable amounts of time under minimal load. I updated to the latest image available 6.3.5 and the latest pdm 3.0.4 but still had issues. Decided to revert back to 6.3.1 and the PIX began to hang after only a minute or so. Then tried to update back to 6.3.5 and the PIX hung mid flash. Now it just constantly reboots. When I try to tftp either of the images I get a checksum error and then it begins asking me for an activation key (which I don't have, nor a copy of the previous running config). what next?????