OS : FreeBSD 8.2
Hypervisor: VMware ESXi 5.0
The clock on our FreeBSD webserver suddenly stopped. This appears to be a bug in in ESXi 5.0.
To fix this:
If the time counter is using HPET then change this to ACPI
Note: The setting doesn't persist after a reboot so make sure you put the following line in /etc/sysctl.conf
Edit: VMware have actually released a patch for this: KB:2021185