4ondemand - not playing downloaded shows?

[PeteG]

I've downloaded a few episodes of Teachers, but when I go to play them, it says "Ready", but clicking play does nothing... am I being a clot, "help" only tells me how to select different window sizes. Is there a "play in external player" option for downloaded shows, like on iPlayer?
Am I asking too many questions?

[Scraggles]

http://www.channel4.com/4od/get4od/index.jsp

Did you install the player ?

[PeteG]

I've only just installed it, previously used it to watch another show and it worked fine. Now, nothing will play - even when I disconnect from the internet and try to play things offline.