Older thread, but there is a solution that doesn't involve arbitrary reboots just to clear this. It does seem to be an issue with expect, and these steps resolved it on a box we manage that was having this issue:
First, make sure you do have /dev/ptmx and do make sure it is chmod 666. On most standard compiles, this should exist and be correct already. Second, ensure you have a directory /dev/pts. If it doesn't exist, create it. Third, put this into your /etc/fstab:
none /dev/pts devpts gid=5,mode=620 0 0
Lastly, mount the devpts filesystem:
mount -a
And that should do it. Note that your kernel compile must support the filesystem. If you run
cat /proc/filesystems | grep pts
and nothing is returned, you'll need a recompile to add that support before doing any of this.