Apparently the one and only 10.9 slave found some new and exciting way to get itself stuck. According to https://secure.pub.build.mozilla.org/buildapi/running it is currently running jittest on both 68590c6c1ff7 and de1a3b3fbf4e, having started those runs one second apart at 2013-12-05 21:13:59 and 2013-12-05 21:14:00. Not only is that quite unlikely, but it doesn't seem to be going well for it, since that's over a day ago and it isn't doing anything else.
Attempting SSH reboot...Failed. Attempting PDU reboot...Failed. Filed IT bug for reboot (bug 1008364)