When running a Lotus Domino Server a wrong time can be very annoying, just imagine you have some agents not triggered at the expected (real) time. I have seen some Operating System time drift especially with Linux virtualized into VMware. I made some google searches and found that this problem seems to be quite common and there is lot of information on that issue.
I found a solution that works for me, which is to edit the boot options settings to add the following parameters:

acpi=off noapic nosmp nolapic clock=pit

As reported here Novell is owning the copyright on Linux, not SCO. I think this really makes the suit SCO against IBM look senseless.

Due to the fact that IBM Lotus Domino 6.x was released some time before Windows Vista was released, there was no support for Internet Explorer on Windows Vista. A couple of customers asked for a fix for Domino 6.x so they do not have to upgrade to Domino 7.x to solve the issue. A Fix for Domino 6.5.6 FP1 is now introducing this support for DWA on Vista.

More Information from IBM: http://www-1.ibm.com/support/docview.wss?uid=swg24016489