ESXi 5.5 Update 1 and NFS APD fix
VMware has released a fix for the problem with disconneted NFS Datastores in ESXi 5.5 Update 1, with Express Patch 04.
See more in the VMware KB about the problem: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2076392
And the Express patch discription can be found here: http://kb.vmware.com/selfservice/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=2077360
I have not testet this patch, so use this information as is.