ATI released a Catalyst 4.12 driver (beta) on the same day they release 4.11 which seems to fix a small bug:
"Random hanging has been observed with certain games on certain systems when using the PunkBuster server. To resolve this issue, please download CATALYST 4.12 Beta Release which resolves the majority of cases of this hang."
In contrast, our forums report that these drivers 'might' have HL2 performance improvements. For now this just seems to be a punkbuster hotfix.