On the PBX-IP Media Gateway (PIMG) 5.0.52N firmware, a password works fine, but after the firmware is upgraded to 5.1.70, the same password does not work when an attempt is made to log in through the web browser. The nine digits of the old password work when an attempt is made to log in through telnet, but the same nine digits do not allow access to the web browser.
This is a known issue with the 5.1.70 firmware.
In order to resolve this issue, log in with the nine digits of the original password through the serial connection and reset the PIMG to the factory defaults. This provides the ability to access the server. The issue with this firmware is fixed in SU1, which is not currently released.
The only way to perform the upgrade and retain the password is to change the password to eight or fewer characters before the upgrade process.