Straight from : http://community.spiceworks.com/how_to/show/662
I’m using ESXi 4.0, and i was facing the problem of “Another task is already in progress” error, practically the VM could not be used at all (turn on restart or even force off).
in ESXi 4.0 SSH console, using the command “service mgmt-vmware restart” will do no good :-(
therefore the solution is by using: services.sh restart command, quite simple and it doesn’t kill the whole VM process which is currently running on production, the only thing that is affected is the VCB backup, it failed when that command issued. Finally in your vCenter console, right click on your ESXi host in which you run the command and then click on reconnect.
So on the ESXi box hosting the troubled VM run;
services.sh restart
Then reconnect to that ESX box via VI Client. Shouldnt effect any of the other already running virtual machines.