I've seen a little of this error on here, but not specifically from vCenter. In the FAS3270 and FAS2240 logs I get:
[HTTPPool01:warning]: HTTP XML Authentication failed from <IP of vCenter Server>.
In the vCenter Server, I'm getting:
[btpool-2] ERROR com.netapp.smvi.security.authentication.vsphere.VSphereAuthenticator - Failed to authenticate vSphere sessionId %s
And then a whole bunch of other lines with apache server errors, etc. If the details are important, I will copy it over to here. Just let me know.
Michael
esxguide.blogspot.com/