Bash auto-completion with added spaces – why, and how to fix?

Solution 1:

This is a known bug. See this LP question and these bugs 1 2.

This comment seems to be the fix. If you can't wait for a fix to trickle down the normal channels, edit /etc/bash_completion line 1587, change default to filenames (make a backup first).

Solution 2:

I had, and solved, the same problem after installing Adobe Reader on Ubuntu 12.04.

I commented out the _filedir block in /etc/bash_completion.d/acroread.sh and it worked normally again.