Powerconnect 7048P Stack 'System Power Status - Error'

I currently have a stack of 4 7048Ps in production working perfectly. Although when entering in 'show system' or 'show system power' in the CLI the Power supplies section currently only gives me the information of the master switch and the other 3 are Status: Error with no information. 

1 System Error 0.0 0.0
2 System Error 0.0 0.0
3 System Error 0.0 0.0
4 System OK    4.2 72.4

Entering show switch stack-ports shows all stacking cables working at 16Gb/s.

Any ideas as to how i can get the information of these other 3 switches? as we are just about to roll out VoIP phones to them and I need those statistics.

Thanks.