time problems

[bram]

Hi all,

I am running 6.1-RELEASE-p2-AMD64 on a dual AMD opteron system.
Lately (after installing a twa-3ware raid controller I think) time just 
stops.
We leave at work one evening and the clock is set ok.
The next morning the clock is set at 3 o'clock instead of 8 o'clock, 
sometimes there is no clock anymore,
when we type date, it just returns to the next line without any output 
whatsoever.

This is very annoying, I've set a crontab task every 5 minutes to 
re-update the date but it does not help (wich leads to my believe that 
time has stopped).

So, what could this be, and can I work around the problem ?

Every service this machine runs stops working at such a time (no ssh 
etc), the local keyboard still works.

kind regards