Did the human data set name change? I can't find it al all under listDatasets() either.

EDIT Reinstalling biomart fixed it for me. A colleague of mine had the same issue so not sure what caused it...

This was caused by some of the new primate datasets including apostrophes in their descriptions, which biomaRt was unable to handle.  This has been patched in both the release and devel branches (2.34.1 and 2.35.2 respectively).