Similar case here. Upgraded one ESXi 5.1 host from build 914609 to 1065491 and the host became failing to attach any existing datastores in our compellent disk storage - newly created volumes were ok; and connectivity to other two storages from other vendors were also ok. Neither compellent nor vmware support were able to find the culprit. I'm going to restart the compellent next Monday (which fixed a similar problem 6 months ago). If that still failed, I was advised to rebuild the host using the pre-U1 5.1.
Alfred