Make sure the bike really fits - especially make sure that your seat height is ok.

If your seat height is off, especially if it is too tall, you will really see a difference at higher cadence. If the seat height is too tall, you will really wobble as your hips will have to rock to let your foot reach down for the bottom of the stroke.

I would think if the seat is too low, you might feel more pain at higher cadence, or something like that.........