Beta launcher hangs during "Checking for updates"

Just tried to crank up PA and am getting stuck on the "Checking for updates" screen of the launcher. If I cancel, it then sticks on "Cancelling". But I can't play or verify files.

Update. Okay, so it eventually finishes with "Update incomplete...please verify files" which, when clicking Verify Files then returns to a very very long "Checking for updates" which eventually ends in the above, giving an endless loop of fail. :-(