Superfish problem

I’m using the free Swatch theme from Woothemes.

On normal pages there’s no issue with the Superfish menu, it displays arrows beside nav items with children eg http://www.ballykeigleps.org.uk/index.php/education/educational-themes/

However, on posts the menu doesn’t work as expected with no arrows displayed. More problematic is that the auto thickbox plus plugin doesn’t work with IE8 showing a JavaScript error I don’t understand eg http://www.ballykeigleps.org.uk/index.php/2011/10/28/save-our-smiles-2/

I’ve tried comparing the source of both pages but can’t see any difference and both are using the same .js file. Can anyone help at all? Many thanks!