I go to the download page, untick the boxes as I don’t want to be contacted, click the Download button and I’m taken to the Unity Overview page.
Any links I’ve found to download Unity, usually end up in my going round in circles between those two pages.
I’m using IE8 in Windows 7, and have also tried compatibility mode.
OK, I’ve just tried an XP machine with IE7 and the download works, so there must be something in the page which doesn’t like IE8 and/or Windows 7.