In IE7 on two different machines, - one XP, and the other Vista, the following happens for me:
If I freshly load or reload the page into musicProduction/index.php I can click on the 'Services', 'Web Design', and 'Home' links, and the menu works just fine. If, from any of these pages, I click on the 'Music Production' link, it will open that page, but from then on the menu doesn't function for any page.
This is odd, as I would assume that the menu and other page elements in the musicProduction/index.php page should exhibit the same behaviour whether it is from a freshly loaded page, or from the page as arrived at from by clicking the musicProduction links (on any page). Same page, but two different behaviours.
In IE8, the links don't seem to work whether in a freshly loaded page or whether it is arrived at through any of the links.
This by way of information, nothing practical, but will have another look.