This post was a symptom of a larger problem with the F15 kernel and HFS+ disks (my second computer is an Apple Macintosh). I posted a bug at Redhat's bugzilla
My follow up here is to point this forum post towards that bug. Also, as of
Fedora Kernel (184.108.40.206-0.fc15.i686)
the problem still persists, albeit in a slightly modified form, even though the powers that be closed the bug.