This is a simple fix for some of the problems with bad ACPI frequency values:

  Abort if the frequency field in _PSS is zero, as we're having a
  completely broken ACPI table then.

A more complete overhaul of the acpi-cpufreq driver (where the cause of
the problem lies) is in the latest acpi-test tree, but that's definitely
something to be delayed for 2.6.3 -- and the same is true for the
yet-to-be-written do_div64 conversion.