As a part of a recent data center move we had to reconfigure several APC management cards. The first thing that I did to each of these NMCs was to reset to factory defaults and update the firmware.
This is a fairly simply process normally. Connect the appropriate serial cable, connect to the comm port, press the reset button a couple of times, and log in with the default credentials (http://www.apc.com/us/en/faqs/FA156075/). Once logged in, you can use the command to factory_reset or format the card and bring it back to factory settings.
In one case, however, the card didn't survive the factory reset. In fact, it appeared the card had started to boot, but never finished the booting process. By changing the baud rate around in my settings, I was able to connect to the BootMonitor using 57600 baud, 8 data bits, no parity, no flow control. It was also at this point that I saw an error related to the checksum of the AOS firmware which was preventing the card from booting. We had another NMC that I could swap to if I needed to, but I wanted to see if I could simply reload the firmware onto the card and get everything working again. Fortunately, APC has an article for that: http://www.apc.com/us/en/faqs/FA293874/
Using TeraTerm and XMODEM, I was able to upload the bootmon, AOS, and application module firmware files (in that order) to the NMC. Once that had finally finished, simply rebooting the NMC brought everything back online.
This also had the positive side effect of updating the firmware on the card because I wasn't able to download old firmware files from APC's support site. From there, I could complete my setup process and bring everything back online.