Pan tool bug when making a selection

When I am making selections and using the spacebar pan tool combo, sometimes it works and other times the pan tool won't appear such that I have to drag the selection marker around the screen. It's very off on and doesn't make any sense as to why it works sometimes and not othertimes.

What's really irritating about it, is you don't know the pan tool space bar function is not working, so you make a long selection thinking it's working, but go to use the pan tool and it's not there so it scrambles what you are doing ruining the selection you just made.