I too am getting the same 'LOADING' screen when either running the BBC iPlayer App, or attempting to watch any BBC show from catchup.
This only happens from the main Humax 360 box though, the 360 Mini runs BBC iPlayer without any issues.
I have only just installed the 360 boxes this evening, replacing 2 x v6 boxes and all other apps seem to work okay from both boxes.
With the problem possibly being widespread amongst 360 users, I trust VM have this in hand to offer a quick resolution.