I get this message when there's been a bad *disconnect* from a fuse fs.
Unmounting and remounting the fs solves it
Code:
$ fusermount -u <mountpoint>
$ sshfs <mountpoint>
hth,
edit - apologies for posting an inappropriate solution (I re-read the OP and realized that it had nothing to do with fuse), however I'll leave the post intact, as it may help someone else...