I have just setup a brand new install using the latest wordpress, buddypress, blogs mu theme and ultimate facebook.. I read that you thought it was due to js errors so set up a completely untouched, brand new install..
You can view it here http://my-city-social.co.uk/
When trying to log out of wordpress, ultimate facebook first logs out of facebook.. You then have to log out again which in turn logs out of wordpress...
Any chance of getting this sorted?