I've had something similar when the boarding pass reader was acting wonky ... it was taking 20-30 seconds (+/-) to log each scan so she was asking names to check if the computer display had caught up yet -- basically, was the screen display in "real time" or was it delayed?

Sometimes, it really is that simple.

Had exactly this about a month ago in IAH -- the terminal construction seemed to really be messing with some of the gate connectivity. Felt awful for the staff - they had their hands full and then some in a terminal that looked more like a bare-walls prison than even a bus depot.