On Windows I want file completion with <C-X><C-F> to use forward slashes so I say 'set shellslash' in my vimrc. Lycosa buffer explorer doesn't play nicely with this. If I open a few files, set shellslash and open the explorer then the files just don't show up and the explorer is one line tall. Unsetting it then reshowing the explorer works fine.
I guess this is somehow related to your frequent use of os.path.sep in lycosa.py.