Hi Alan, Icon...
It's happened with Iron/Vista, too. Even without the "restart"... if what I saw is the same as what Alan is referring to. Has only happened during single play to me.
The entire upper-left window (Menu, Friends, Invites... along with my player's name, etc...) is gone. I've seen it "missing" for 3holes, after which it comes back on its own.
Perhaps you (Icon) can confirm... Is WGT experimenting with this area of the GUI? Maybe an "ON/OFF" switch for the Friends list is in the works? :)
Inquiring minds want to know. ;)