well first off its a good thing to wax your skis monthly. Also it might be your edges depending on how sharp they are. If they're still as sharp as the first day you got them then just take a file and file down a little bit of the edge underfoot.
Most of the time though its just the rail thats sticky. A lot of it has to do with weather, if its warmer out then rails are more likely to be sticky and vise versa.