Ubuntu – A mount of box.com as davfs2 hangs and does not become unstuck

I have mounted box.com on a Ubuntu 11.04 system, and it worked fine. For a day. It is mounted with the davfs2 file system. But after a day it froze, and all shells that try to list or do anything in the parent directory of the mount point freezes.

I have read on serverfault that a reboot might be the only way to resolve the dreaded "D" IO probmem (reuqest_wait_answer). Which is fine if it happened only once. But more interesting is what caused it to hang and how I can prevent this in the future. This is how I mounted the point

https://dav.box.com/dav /home/myuser/box.com davfs rw,user,noauto 0 0

I bring that up because I don't have the overview of all options to the module, maybe something will help?

To sum my question up:

1. How do I unstuck the stuck davfs2 share when all operations (including mount -o remount and umount) just freeze?
2. How do I prevent this from happening in the future?