Out of control disk usage.

I have BackWPup running on a Linux Ubuntu LTS server. It’s configured to automatically ftp the backups to an offsite server. The backup runs weekly. The problem is that over time, my disk space disappears.

After investigating it, I found a file without a name in in the root directory of the site. See this image: http://img69.imageshack.us/img69/948/wnw.png

The only way to access the file is through its inode. In the next image, you can see that I renamed the file (actually a directory) using it’s inode. I change into the renamed directory (oddball) and traverse the tree to the bottom where I find a backwpup zip file and a few others.
http://img17.imageshack.us/img17/858/gsx.png

On each run, the backup includes this bogus directory so it grows exponentially, eventually consuming the entire disk.

I’ve been seeing this problem for several version and just working around it by deleting the bogus directory but it’s become difficult for me so I need a better solution.