The data buffer created for the "VMware" service in the "C:\Program Files\VMware\VMware Server\vmPerfmon.dll" library is not aligned on an 8-byte boundary. This may cause problems for applications that are trying to read the performance data buffer. Contact the manufacturer of this library or service to have this problem corrected or to get a newer version of this library.
According to Microsoft: "Windows requires performance counters to conform to 8-byte data block sizes. The specified service does not conform to this requirement. Contact your software support provider to obtain an updated version of the service."
It is not clear what implications this really has on performance monitoring. For example, despite this Warning I was able to monitor performance counters from the VMWare source just fine.
From my experience this warning can be ignored in most cases.