Can't force unmount device

["Dr. Jennifer Nussbaum" <bg271828@yahoo.com>]

I know this problem has been discussed endlessly online, but i cant get any of the suggestions to work.

I have a Debian laptop that, when im at home, I mount via nfs to a local fileserver. Sometimes for no clear reason, i cant unmount it, and when this happens, i cant put the laptop to sleep. There's no swap on this drive, and it's not an encrypted filesystem. There are no symbolic links pointing to this device. I dont think anything is accessing the device, and I'm not in a directory on this disk, but nothing to figure this out works:

  $ sudo umount /mnt/RemoteDisk
  umount.nfs: /mnt/RemoteDisk: device is busy
  umount.nfs: /mnt/RemoteDisk: device is busy
  $ sudo umount -f /mnt/RemoteDisk
  umount.nfs: /mnt/RemoteDisk: device is busy
  umount.nfs: /mnt/RemoteDisk: device is busy
  $ 

So i try:

  $ sudo lsof | grep Remote

This hangs, as does a simple lsof.

So i try:

  $ sudo fuser -m /mnt/RemoteDisk

This also hangs. So does:

  $ sudo fuser -u /mnt/RemoteDisk

I end up having to power the computer down, which is extremely annoying.

What could be causing this? Ive googled this up and down but still dont know what to try.