I hate running into invisible walls. In my apartment we have a hallway that runs from the livingroom to the bedroom. I have lived here for several months and use that hall regularly. Then for no apparent reason, I can not walk down that hall any more. I can see then floor and the door to the bedroom. And google is no help. Searching for "cannot walk down hallway" returns 273,000 results that don't help me.
finally after spending the day trying to get down that hall, I discovered it was a invisible wall. I know it was not there before because I walked down it yesterday. Now that I know it is a wall I can remove it. Problem solved.
When I find these invisible walls I almost scream. My blood boils.