SLK 230 steptronic problem

Hi All. Having probs with my SLK 230's steptronic, insofar as the steptronic is not working anymore. Tip the in 'D' as much as I like, and nothing
happens. This is a pain, as it's a feature that I use regularly enough. It happened once before, about a year ago, but it cleared up of its own accord. I reckon this is a problem that need not be specific to SLKs only, but any Merc with a steptronic autobox. The car was bought from new in 2000, and has been as good as gold until now.
Anybody got any ideas?
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