In most cases it is not a regression, but rather the usual kernel
API/ABI change.
Marko,
In this case, the kernel API has not changed. The changes between 166
and 168 were to patch vulnerabilities (and some small other changes):
http://lists.fedoraproject.org/pipermail/package-announce/2010-September/...
I believe just the glue between the kernel and the binary ATI driver
needs to be recompiled (correct me if I'm wrong).
Thanks,
Daniel