jQuery Doesn't Work on index.php

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New Member
This is a link to a new portfolio site, I'm currently working on. I have added some jQuery to my header.php (for the thumbnail rollovers) and it works fine on all the pages, apart from the index.php page.

I really can't figure out why it won't work there.

Can someone have a look and maybe point me in the right direction to fix this problem. Thanks.