Can anyone identify this IE7 bug? [HTML / CSS]

Hi everyone, I have recently been working on my webite and have noticed theres a bug in IE7 (I havent actually got round to sorting it for IE6 yet!!). Basically the list items when you click ‘Browse by Media’ or ‘Browse by Client’ dont display as I intend. It seems there is some kind of issue going on which I can’t quite identify. If anyone can spot this issue (text is cut off) and suggest where to look for a work around that would be great.

Heres the link:

You need to click on Browse by Media or Browse by Client to reveal the problematic list.