.. just realized you downloaded films from Google Play. I download movies from file sharing sites whereas you download from an 'official' site. It's unlikely that an official site will download a file that is in the wrong format for your Archos.
We followed some directions we found on mumsnet re getting Google Play app downloaded and getting films downloaded is no problem, but we have found they dont play :<. Two very sad dd's for long car journies. Otherwise, we are plaesed with these tablets but would like to be able to solve this issue. Anyone out there with any wisdom?