Just tested. Appears to work for me.
:mbx, can you provide the test case we had from the other day?
One way this can happen is if the markers don't match -- either the start and end strings differ, or the recording is stopped before the end marker is emitted. See bug 1104202.
:mbx, reopen if you can provide STR and test case.
Sorry for the spam. Moving bugs to Firefox :: Developer Tools: Performance Tools (Profiler/Timeline). dkl