It is quite interesting to try and photograph anything on a window as the camera wants to take a picture through - as opposed to of - the window.
1/12/09 NOTE: We figured out why only this one window had the frost. There was actually some condensation in between the inside glass and the outside one. As this is not how it ought to be, we just had it fixed about a week or two ago. No more frost. :-( (Glad we saw it and got the pictures while we could!)