There was an interesting study result released by Johns Hopkins a couple of weeks ago. This research was not directly related to autism but instead has tangential interest.
The study focused on mice which had a genetic sequence linked to schizophrenia in humans. It was basically looking at environmental factors (specifically inducing a virus or parasite type illness)
The results were interesting in the fact that the mice that were introduced to these environmental factors as foetuses had increased anxiety, symptoms of depression, altered social behaviours and weakened stress responses.
basically what this shows is that a single genetic variation believed to cause a specific illness could under environmental factors produce entirely different illnesses. The researchers intend on also varying the timing of the introduction of the environmental factors to see the effects.
Also should be noted a control group that was not introduced to environmental factors did not develop these symptoms.
This does lead strength to the faction that does believe that environmental factors as well as genetics could be the actual cause of autism rather then just genetics or environmental factors.
I believe further testing would be required and would also expect that this theory will come under extreme fire as does any test linking any form of environmental factor to autism. Time will tell whether the results of this testing can be replicated by other labs.