OMPC 'Protocol Operation Failed' on DRAC6 units

hi folks,

we have a whole bunch of Dell Poweredge boxes, but the ones i'm having issues with are our R710's with DRAC firmware version 1.97 & 1.98.

within OMPC, I have discovered these six devices previously and have managed to obtain power/thermal stats from all of them, but for some reason, the stats only seem to run for about half a day before I encounter a flood of errors in the event log stating 'Unexpected protocol error(s) have occurred. Retry the operation, and contact Dell support if the problem persists.'

IPMI over LAN is enabled on each of the DRACs, and we are using a 40-character encryption key. I have attempted:

• upgrading the firmware on the cards from 1.97 to 1.98
• removing the encryption key and sticking with the default 00000..etc
• deleting the devices from the devices list within OMPC and re-discovering them with a new protocol to reflect both the old and amended encryption keys

the strange thing is that OMPC can happily discover the devices without issue, it just refuses to pull through power/thermal info for extended periods of time.

of the cluster of six servers, three are running Windows server 2012, the other three make up part of a Vmware 5.5 environment.

the statistics stopped coming through at a point yesterday when nobody was left in the office to even make changes, the only thing we've amended since they started taking stats is the frequency at which it polls (from 1 minute up to 10)

I'm not particularly good at explaining things, my apologies, but any ideas?

thanks,

Tom