I've seen other people report this.

When I use mouse button 4 (free look mode) the camera just spins continuously anti-clockwise. I thought this might be because of my old mouse, so I've bought a new one - a Logitech MX518 gaming mouse.

Guess what - the problem still happens.

I assume that this is a bug with the game, and hope it gets fixed in the patch. Use to work fine in RTW.