Usually, when it says "BIOS BUG" it indicates a BIOS bug. Have you tried updating the BIOS if possible ?
But, I think there is a fix for it, and this message tells you that the problem has been fixed or handled by the kernel without incident.
See the wiki an time stamp counter:
And this article:
Current AMD Opteron(tm) and Athlon(tm)64 processors provide
power management mechanisms that independently adjust the
performance state ("P-state") and power state ("C-state") of
the processor; these state changes can affect a
processor core's Time Stamp Counter (TSC) which some
operating systems may use as a part of their time keeping
algorithms. Most modern operating systems are well aware of
the effect of these state changes on the TSC and the
potential for TSC drift across multiple processor cores
and properly account for it. Although cores may drift with
respect to one another, an individual core's TSC is always
monotonically increasing. This drift can *not* occur on
single-processor single-core platforms.