2008.11.27
I could not manage this device because I didn't know the login/password for it and I had no idea what it's current configuration was.

Find and download the 3Com Software Update Utility and the switch software - you'll need them. You'll also need a 9-pin serial cable.

Download and install (on windows) the 3Com Software Update Utility
and the switch software.

Time for the big switch!

DANGER!

This will nuke your current configuration and delete the installed switch software. This is an unrecoverable action!!!
Login as 3comcso, password RIP000
Do you want to re-initialize this device(y/n) [n]:
If you type 'y', then you'll completely nuke the switch.

Turn the switch off.
Run the 3Com Software Update Utility, give it the location & name of the switch software when asked.
The Update Utility will prompt you to power up the switch and the update will commence. Mine took about 2 minutes.

When it's done, power cycle the switch.

Start HyperTerminal (windows) or Minicom (Linux), configure your session for 9600,8,N,1.
Hit [Enter] a couple of times and you'll get a Login: prompt.

You can now login as manager password manager

That's it - you're in!