I'm sure this has been reported several times, but I didn't want to search the forums all day.
When selecting a friend's profile, a popup window opens to display the new content... or at least it tries. If you have an existing IE window already open, that window and your WGT window lock up and stop responding. Only after you crash the existing window, will the popup be allowed to open. This also happens, I found, when you first login and choose Play Now. I imagine it's anytime you get a popup and already have IE open. It shouldn't be a IE setting since it's not an issue popping if you don't have that existing window open, or if you log into a game first.
Either way, the popup window should not be attempting to activate an existing window.