I am seeing the same problem.
I am able to manually set a preferred path on our ESXi 4.1 host through our newly installed VMware vCenter instance . What I am not able to do, however, is to use the virtual storage console 2.0 plug-in for VMware vCenter to set the preferred paths. It looks like the vsc was installed and configured correctly, because I am able to add storage controllers and I can see through the manage plugins window that it is installed.
The problem behavior can be seen here:
As you can see, there is an alert in the MPIO settings, and whenever I try to “set recommended values,” it errors out on the MPIO settings portion. Also, when I go to the show details command here, it shows many details in green which seem to be correct settings, the only setting in red is the following:

Any ideas on what could be the issue? I have already opened a ticket with Netapp support but they haven't gotten back to me yet.