The x264 package fails to handle two-pass encoding properly. The first pass will generate what seems to be an invalid stats file, which is then rejected by the second pass. I only had time to test this with a couple of files, but upgrading to the 07-10-2006 snapshot seemed to solve the problem. The stats files generated by the newer version were larger by 7-10MB, so the difference between the way the versions handles this is clearly significant - which is a strong suggestion that updating to a newer snapshot is appropriate.

Since all that is required is the changing of the snapshot date in the PKGBUILD, it is very easy to update the package. It's been quite a long time, so IMO that's what should be done. I didn't just want to flag the package out of date though, since the meaning is unclear with development snapshots.