3Com Super Stack

I have stack of 6 4400pwr 3Com switches, i find that 5 of them uptime is 200 days and they other one im the middle is 0 days, meaning that its dropping power at some point, all of the switches are bought at the same time so they are new and not filled with dust, or something like that!
i have swapped the switches around thinking that it could be a faulty one, but no the one in plaice is dropping power! now did any one come accross this problem? i have tried all sorts.
thanks