I was trying to power up a new VM on an ESX 3.5 host just now and I got the following error:

“A general system error ocurred: The system returned an error. Communication with the virtual machine may have been interrupted”

Nice and helpful!

It appears that there are two ways to fix this. The first is to reboot your ESX host. Of course this isn't normally practical and you may have VMs running. The alternative is to make your way into the service console and issue the following command:

service mgmt-vmware restart

Assuming that no errors are displayed as the service is restarted you should be sound as a pound (although these days the £ isn't worth much).