iPlayer Problem

[Region3]

I'm having problems with iPlayer and wondered if anyone else had come across the same thing or might be able to offer any suggestions.

Live tv works fine.
Live radio works fine.
On demand tv works fine.
On demand radio gives me an error something along the lines of you do not have sufficient bandwidth to play this program

Surely I need more bandwidth for streaming video than audio?
It doesn't make any sense to me.

All suggestions gratefully received.

Thanks.