The thing is that your refs/heads/critbit says that ce8ecbed625b14643e67e114c904e58320907579 is the head, but apparently no such commit object can be found in objects/?
And no, fetch still isn't working. Making a new clone seems to work though, and gets this object. Very weird. Well, that allows me to work around the problem at least (by fetching from the new clone first)...