Comment 36 for bug 159031

Gutsy? I have the same problem in Ubuntu 11.04. There's also an ugly workaround.

Problem:

When the remote computer mounted with sshfs loses the connection, the local computer (Ubuntu 11.04) freezes all related processes (but not the entire computer) indefinitely. That means usually Nautilus freezes first, and the Terminal Emulator freezes second when you try to tab-complete the mountpoint for the umount command line.

Workaround:

If you go to a different TTY (ctrl+alt+F1) in stead of a Terminal Emulator, tab-complete will have no problem. You can
umount --force /mount/point
It will fail, but repeat a bunch of times and it will unmount.

Switch back you your X session and all your resources are released and functional.