There are 2 documented causes of the Metro tiles not working when clicked on:

1) If your screen resolution is below 1024 x 768 the Metro tiles will not work. Right Click desktop and choose Screen Resolution. Set it higher. This might be a problem with smaller screens.

2) If you shut UAC completely off, the Metro tiles will not work. Control Panel, User Accounts, Change User account settings. Move the slider up to at least the lowest setting.

It's very difficult to evaluate the Metro UI when the tiles are not working. Yes this is a radical change, and yes I feel much more comfortable with the Classic UI, but because I am trying to learn about Win 8 and how it works, I have turned the Metro UI back on. Yes I had to put UAC to the lowest level to allow tiles to work. Since my screen resolution is 1600 x 900 this is not a problem for me.