Hi Terry: The most likely cause of your binding problem is that your rip fence is moving. I had the same problem with my cheapie Craftsman 10" TS. On large pieces of plywood I had to wind up clamping the rip fence to the table top to keep it still. Also, be sure that the rip fence is running parallel to your blade. You can do this by running your blade all the way up, then measuring the distance from the front edge of the blade to the rip fence and the back edge (the edge nearest you) to the rip fence. Measurements should be identical.
It is also possible (but much less likely) that there is play in the bearing on the shaft that the blade bolts to. You can subjectively 'feel' this by first unplugging your saw, then run the blade up as high as it will go, and then grab the blade with both hands resting on the table with the blade between each thumb and index finger, and rock the blade back and forth. You should not be able to 'feel' and play in the bearing. If you feel any kind of mechanical, metal-to-metal clunking, the bearing is bad and will have to be replaced.