Hi Frank!
I had similar problem with my EOS 350D. I cleaned the sensor
(I think mines behind a little piece of glass, so I cleaned the
glass?) and in a few days new dust spots appeared. I never
thought the shadow may appear when theres no dust particle,
is it possible? Since that I don't bother with them, when
necessary I just edit them with software. I even got one lens,
and to think what will happen when I acquire some more
Cheers
Pedro