We had I similar problem on on of our aircraft(757) when extreme over pressure from the bowser caused the internal refuelling pipe to split, resulting in a large fuel spill. Luckily the fuel did not ignite and was finally dealt with by the airport fire service.
The interesting fact that emerged was that the captain is responsible for the continuous monitoring and supervision of all refuelling operations i.e. Himself or his representative should be outside throughout the refuelling proceedure to ensure all regulations/safety proceedures are being carried out. How often do you stay and watch ?.