If I make a cellular connection, that sometimes happens to me. The phone takes its time establishing a link (I don't keep it data connected all the time), and that may cause some kind of problem for the maps downloading thread. Probably a timeout in an opportune place -- in some other places, it waits much longer.

That's quite different from what happens when downloading routes. That process fails with a "could not connect" immediately when pressing Ok in the route dialog, despite the link being established in the background. I've learnt to wait in the dialog for the "Phone connected" message that tells the OS finished the link negotiation.