I'm using cryptmount-4.0.2 on Ubuntu-server 10.04. I've a volume that I didn't unmount (with cryptmount) before logging out with the user owning the volume. As a consequence, the volume remains mounted and it cannot be unmounted any more because it is supposed to be busy according to cryptmount -u. I already check that no process is accessing the volume with lsof and even try to unmount it as root.

The only way of effectively unmounting the volume was with "unmount -l" and rebooting (maybe removing the device from /dev/mapper/volume can also works instead of rebooting).

I wonder if this is a bug or simply an user mistake. Any case it could be great if I can help you to debug it.