The at rpm shipped with FC1 is affected by this bug.
http://bugzilla.redhat.com/bugzilla/long_list.cgi?buglist=112430
Namely that at jobs run from non sh/bash shells (or with SHELL set to a csh-like shell) fail.
The at-3.1.8-53 SRPM from FC2 can be made to work by editing the SPEC file to define WITH_SELINUX as 0, and editing out the patch23 line before building.
That's probably not the most correct solution though. Can someone who speaks .spec better release an update for FC1?
Thank you.
-dean takemori