In my experience, scanning Pt/Pd throws up all sorts of problems. Paper grain, dust, things that are imperceptible on the print being magnified, things that are obvious on the print being lost, and other irritants (depending on paper and a host of other factors). Most importantly, though, the tones get violently distorted. Pt/Pd is sensitive to the kind of light it's under and scanner lights are about as bad as you can get. (If you've never done this before then try looking at a print under halogen, tungsten, or fluorescent lights and then taking it straight into the daylight - you should see significant changes in the tones.)
I've found the best way to reproduce Pt/Pd prints for online use is to use a copy stand and a digital camera, ideally under plentiful natural light (be aware of the angle of the light as this may exaggerate paper texture). You can use a blower brush to get rid of any dust on the print. Usually all I need to do in Photoshop is to tweak the curves and then desaturate by 20-60% depending on the type of light used.
But even this process is flawed. Unfortunately the bottom line is, I believe, that a digital copy simply cannot show a Pt/Pd print in it's full magnificence.
One thing to think about though... Digital repro can highlight underlying problems with a print which you haven't noticed, so you may want to consider this before blaming your scanner. For example, if you have used too little solution then you can sometimes get a grainy effect...