Google release Google Maps API v.3.27 yesterday and GMLib appears to be broken. When I specify v3 and the current release of the Google API (v3.27) is used, the map does not appear. If I specify v.3.26 in my map.html, the application works correctly.
I am using GMLib 1.5.3 and the problem can be reproduced in the MegaDemo project included in the GMLib files.
You can download the newest version 1.5.4 from here