Assuming you can get access to the sensor somehow, try holding the camera upside down and using a blower (NOT compressed air) and blowing dust off the sensor. I have tried eclipse and swabs on my MarkII 1Ds and actually blowing the dust off worked better. Using the swabs is dicey because you can cause permanent damage.

Also see http://www.calumetphoto.com/ctl?ac.ui.pn=sensorcleaning