A wonderful trait of the aspergers mind is its ability to focus in, and learn the inticacies of a frame of thought or series of actions. Unfortunately, it can only focus on one thing at a time. In a young immature mind this may have a tendency to dissolve previously learned behavior from the concious mind. Rest assured, the old information is still there, it just is not currently accessable, or necessarily interesting to the child with Asperger's.
Science is still trying to figure out how much this has to do with the theory of Autism as excessive maleness.