When I recently rebooted one of our BL620c G7 blades with ESXi 4.1 installed on it I found that the server had suddenly lost network connectivity after the reboot.
A quick check on the console revealed that the Virtual Connect profile that was defined for that blade had not been applied to it. I realized that because the MAC addresses of the NICs had not been overwritten with the virtual addresses of the Virtual Connect profile.
I tried powering down and up the blade, re-assigning the Virtual Connect profile multiple times, all to no avail ... Then I had the idea that it might be related to the iLO-board of the blade, and - yes, indeed - after resetting the iLO3-board of the blade the Virtual Connect profile was properly applied and all was fine again.
While later looking on hp.com for some related information I stumbled over the Customer advisory c02820591 that described an issue with the Virtual Connect profile being lost upon an iLO3 reset. Not exactly the issue that I had, and the advisory also stated that this is fixed with iLO3 firmware version 1.20, and that is already installed on our iLOs. However, the advisory confirmed my assumption that the Virtual Connect profile is applied by the iLO-board.
So, if you have similar problems try resetting the iLO-board before you start pulling your hair out, or the blade out of the chassis ...