My connection, in general, is the same as Ian's. Mine is through Verizon, ethernet to an Apple wireless, and laptop connected through WiFi at home. Same issue on both connections. I also take my laptop to an other WiFi location and get the same thing.
I also have no issues, so far, with any other Adobe services.
One thing I did notice - when I first installed the software, I did not get this problem. After going to something else (without quitting Muse) and coming back, the problem was there and has been ever since.