Tablesaw alignment puzzle

I have a problem with alignment on my tablesaw crosscut sled. When I cut on the right hand side of the blade, I get a satisfactorily square cut. When I line up to make the cut on the left side of the blade it is not square. I've checked everything I can think of for square. The fence is straight. The blade is parallel to the miter guage slots. The fence is 90degrees to the blade.
Any suggestions?
David