I really recommend updating your version to the newest version, though i'm sure there's no bug for the mediaplay function, you're missing the whole shader features and some other big improvements... As far as your script problem, maybe you should download the newest manual from the download page, and look up the function media_play , because 99% of the functions are explained with a short example, which will definately help you, i'm sure!
Also usually when the engine gives this error, it could mean you did a few things wrong, for example at the end of each line of code should come a ; Or you made a typo or something like that, maybe you can post your script??

Cheers