For all I know running these 49port Hubs fully loaded can and eventually will damage them if you're unlucky.
Seems at this loaded config the port itself requires some cooling.
There are some example images of literally burned components on the PCB of the port due to the high amps flowing through it.
If what I remember is correct, you're much better off running a few less erupters on it, if it isn't already too late.
Other than that, you should check out a plug that has grounding if possible indeed.
-- edit --
Found the thread :
https://bitcointalk.org/index.php?topic=336911.0