clock messed up

Anyone knows a way to fix clock problems which occurs into
kernel 2.6.12-22mdksmp (x86-64)? Basically under
motherboard MSI K8N Diamond, and MSI K8N Diamond plus
(the same happens on three different machines so sound
a problem of our kernel), the internal clock is not
going to be right (and even trying to sincronize
to an external source using NTP is not enough, since
the drift happens anyway). The
differences between internal clock and right clock
goes after one day to 8-10 hours.

I tried to boot the machines specifying on both the option
clock=tsc in lilo.conf, but it's not enough. The error
between internal clock and official time is always high.

Is there a way to fix this? And why ntp is not enough
to keep the time in sync?

Thanks
Bye
Giuseppe.