I don't believe that lightning can be dismissed as a possible factor in this accident. As a glider pilot, I am well aware of the inherent danger of flying into or near thunderstorms, and the following report from the AAIB on the loss of a glider is of interest, particularly, as recommendations are made in the final paragraph regarding the degree of lightning strike protection in commercial aircraft.
See
http://www.aaib.gov.uk/cms_resources...pdf_500699.pdf