Dust or Bad Sensor?

I am new to digital photography and have a relatively new K-10 which I haven's used much until now.

While editing the results of a family vacation picture taking session in New England, I'm now noting a distinct blotch in the upper right quadrant of all my pictures.

I've posted a couple of samples on my website at:

http://www.kcbassociates.com/phototest/index.html

I've tried using the "dust removal" procedure and switched lenses. I've also changed memory cards. However, the blotch remains in all subsequent test shots.

Is this dust on the sensor or is the sensor somehow bad? Never having seen what dust on a sensor looks like, I'm at a loss as to which it might be.

Any opinions would be most appreciated.

Many thanks!