Today, I got an error during upgrade from vSphere 4.0 to 4.1 stating something like: The system call API checksum doesn’t matchThere was a lot of similar lines filling the console. I was a bit worried that the upgrade had gone wrong even though I had done three similar upgrades before this one with no errors - and that I would have to reinstall in stead.Luckily, I found this error description in the 4.1 release notes stating that a reboot will fix the issue. So I waited for a while to be sure that the upgrade finished, rebooted, and everything...