(this started with bug 436855) If loader fails to pull down .discinfo, it tries to unmount the stage2.img that it found previously. When it attempts this, the following happens: INFO : umounting loopback /mnt/runtime /dev/loop0 ERROR : LOOP_CLR_FD failed for /mnt/runtime /dev/loop0 (Device or resource busy) So loop0 stays active. When you get the right URL, it will pull down stage2 and try to mount it again, but since loop0 is active, it fails to mount with an error about LOOP_SET_FD. And then you're stuck. Since we have the normal mount binary, maybe we should let mount -o loop handle creating/destroying loop devices?
Okay, we're using mount -o loop=/dev/loopX now so this should be taken care of. You're still bound to see some similar looking error messages on hdiso installs but that's only because it's attempting to mount images/stage2.img which is not guaranteed to exist on every ISO image in a set. In other words, they should be harmless errors now.
Everything seems to work as expected now.