Only time that sort of thing happened to me was using p2p file sharing, hogging all the bandwidth from the browser but letting MSN go through. If you're downloading anything then that might be causing it, particularly in uTorrent there's a setting which stops it working properly.
If not then all I can suggest is plugging a cable into your computer, selecting the wireless and wired connection in networks via control panel then right click and "bridge connections" while both are connected. It may or may not help. Hope it does
