llSetPrimMediaParams(SIDE, [PRIM_MEDIA_AUTO_PLAY, TRUE, PRIM_MEDIA_CURRENT_URL, url, PRIM_MEDIA_HOME_URL, url, PRIM_MEDIA_WIDTH_PIXELS, 256, PRIM_MEDIA_HEIGHT_PIXELS, 256]);
I'm forcing a refresh just using llSetPrimMediaParams and PRIM_MEDIA_CURRENT_URL (among other parameters).