If with "build menu" you mean the daily action icons visible in city overview, then yes.
I think this can be reproducible only in a controlled development environment, with two developers acting as two different players. One of them donates X - 1 FPs to the other's GB, opens a GvG Map and then the Messenger (maybe in this specific order). After that, the GB owner gives to himself the last point needed to level up while the first player replies something in his Messenger.
If everything happen like it happened to me, the donator will be able to close his Messenger but will have to refresh his browser to get back to city overview.