Please check the VM's settings to ensure that the virtual disk is only mapped once. If this is the case you may want to run vmkvsitools lsof | grep vogsrvr2
from the ESXi host's command line to find whether there's a process running which locks the file. With the output of the command (if any) try to see whether the process ID (the first column) shows up in esxtop after pressing "v".
André