If you try to delete a directory over NFS and get an error such as...
rm: cannot remove directory `asdf/': File exists
... you will notice that conventional methods won't be good enough to remove it.
$ chmod -R 777 asdf/
$ rm -rf asdf/
$ rm: cannot remove directory `asdf/': File exists
Usually there is a file like .nfs234B inside the directory than can be displayed with ls -la
$ ls -la
drwxr-xr-x 2 user group 512 2009-05-20 08:51 .
drwxr-xr-x 3 user group 512 2009-05-19 08:59 ..
-rwxr-xr-x 1 user group 134888 2009-05-18 12:45 .nfs234B
Removing this file only replaces it with another. There are two solutions: manually delete the file on the NFS server, or (if you don't have that type of access) kill its process.
$fuser -u asdf/.\*
asdf/..: 28690c(user) 24845c(user)
9070 is the offending process. Kill it with fire
$ kill -9 9070
Should be able to remove that directory now.