Highway speed downshift problems?

[johnrash]

2003 XC70 135,XXX with a geartronic transmission. When at highway speeds and I accelerate the car hickups or jerks instead of accelerating smoothly. When I put it in manual (geartronic) and downshift it accelerates smoothly without raising the rpms dramaticly. I changed the fluid (3309) last summer and it was on the low end. I topped it off just before I noticed this problem. It is now at the max level (not above) but I don't think this is the problem. Is there a software upgrade that might help? Is there linkage or a sensor that needs replaced?