How are you connected to the WAP when you are attempting the upgrade?
I have seen issues like this when you are attempting to upgrade the firmware over a wireless connection.
Try wiring into the network and doing the upgrade from there. You may also want to try factory defaulting the device and then upgrading the firmware. You shouldn't need to setup up the firmware, I have upgraded several straight to the latest without any issues.
Another thing you can try is to enable remote syslogging and see if the router sends out any messages about what is happening, or possibly what is going wrong with the upgrade.
Hope that helps,
Christopher Ebert - Advanced Network Support Engineer
Special thanks to Alex McDonald for sharing his favorite tip:My favorite
tip is the ‘write default’ command on autonomous wireless access points,
it simplifies manual conversion of a WAP with a static ip address to a
LAP with a DHCP address.This saved a l...
With the latest release of firmware for the WAP 561, 551, 371, 351 a new
feature was added that would allow customers to upgrade the firmware for
their clustered access points from the main access point.The basic steps
to accomplish this is:1) Download th...