Unable to configure NTP on VMware ESXi 4.1

When configuring a time configuration on an ESXi 4.1 you could get the error: Call "HostDateTimeSystem.UpdateConfig" for object "dateTimeSystem" on ESXi failed.

We get this error through vCenter or on the host himself. Additionally we've noticed that the file /etc/ntp.conf is empty.
When editing this file, the contents remains empty.

The solution which worked for us, is to delete this file and to recreate it from scratch.

Example contents:

restrict default kod nomodify notrap nopeer
server 0.be.pool.ntp.org
server 1.be.pool.ntp.org
driftfile /etc/ntp.drift

Now we can alter the configuration from vCenter like all other systems 

Additional information