Enterprise Manager

I'm looking for a solution to the following error with a couple of targets in Grid Control 11g. "Error getting data for target <machinename>. Exception: oracle.sysman.emSDK.emd.comm.MetricGetException: Result has repeating key value : 0 C:".

This is a new GridControl 11g installation. GC installation itself is on 32-bit Windows 2008 server with target hosts/agents being Windows 2008 x64. Most GC targets are successfully sending CPU, Disk I/O and Memory performance data, with the exception of 3 machines which throw the above error. Commonality with these 3 machines is that they all have SAN connectivity. I've tried applying to one of the machines the Windows MPIO hotfix (http://support.microsoft.com/kb/974878/EN-US) as noted in a OMS v10 post I found here but it did not resolve the problem.

I also saw mention of adjusting collection metrics to solve issues with specific data collections but since these machines pull no performance data at all- CPU, disk, or memory, I'm unclear which metric to adjust. These 3 machines seem to provide all other expected data to GC.

Where to look?

TIA.