Trying to upgrade usage allowance

[#1]

Hi,
I'm trying to upgrade my usage allowance at the moment as I've exceeded my monthly limit, but everytime I go through the process it loops back to the start. It goes Choose a new usage allowance, the moves to the confirmation screen. I click 'Buy' to confirm my order and it loops straight back to the Choose a new usage allowance page. Any idea why?
Ta!

[#2]

Hi there,
I've managed to replicate this, and have raised a Priority 1 problem as a result, which you can track here.

[#3]

Quote from: Mand

Hi there, I've managed to replicate this, and have raised a Priority 1 problem as a result, which you can track here.

Thanks very much