Powertap reading correct, downloading wrong

My powertap reads the correct values on the screen, but once i download, my total ride time is usually about 10 minutes greater than what the screen/unit says. I assume that this is from getting off the bike, as I do about twice during a 2 hour training ride. Whatever, I’m cool with that. But what really gets me going is the speed. My average speed today, for instance, on the screen was 14.2 mi/h. on my computer it is 9 mi/h. total distance was like 10 miles less than what I did. Cadence, I think due to the whole time thing, is also deflated. average cadence that is. What the problem is?

On a side note, the PT software sucks. Cyclingpeaks worth the 75$? Can I put my HR data from my polar on there too?

thanks

"On a side note, the PT software sucks. Cyclingpeaks worth the 75$? Can I put my HR data from my polar on there too? "
I think Cyclingpeaks is easily worth the $75, but why do you need to download from the Polar? Isn’t heart rate data included in your PT download?
Have you called Saris to see what they say about the download discrepancy?

Will call tommorow if I don’t find anything out. I generally don’t/won’t race all the time with the powertap, and run the polar with speed and cadence in races. I would like something to have a comprehensive combination of both.