Hi metalazo,
I would suspect it's a bug... you say that one of the WS5100 switches just locks up on you? You need to power cycle it to recover? The switch obviously shouldn't look up, is there anything in the logs that suggests where to look? Perhaps if you attacked a TTY console or printer to the serial port you might catch some error/debug messages that might help you.
Motorola is up to software release 3.3.x so you might want to give that a try. You'll need a maintenance contract to download the software from Motorola's website.
Good Luck
