Sorry for the delayed response! There really is only 1 fix for this that we have found. After doing tons and tons of research, as well as going through lots of pain, the only way we found to do this is with a static ARP entry in the switch infrastructure. I'm assuming that the 2 VMs that are hosting the NLB service are on separate physical hosts, and the port groups and vSwitches that those VMs are attached to have multiple uplinks. This will freak out the physical switch as the NLB mac address will flap between different logical uplinks.
Here are the 2 articles that we used in resolving this.
http://www.vmware.com/files/pdf/implmenting_ms_network_load_balancing.pdf
I'd be glad to help out any way I can if you still have not found a solution. Again, sorry for the delayed response!