FOR SEVERAL YEARS, I used to fly fuel bowsers from main bases to remote locations on planes like the one at left. In fact, I supported one of the airfields featured in the film "Rendition." Those bowsers were legendary for holding sediment and residual fuel. And when connected to fuel pits or fuel trucks, the bowsers often spawned a whole new set of problems (e.g., exposure to sludge or contamination). When BA038 landed short at Heathrow after returning from China, its pilots spoke of having no engine thrust when on short final. That's the same kind of engine reaction I could program into flight simulators back in the day when I was an instructor pilot on the L-300, a four-engine cargo jet. I took a lot of flak for those programmatic decisions because "the odds of (multiple) engines shutting down at once were supposed to be one in a billion." 
According to the Wall Street Journal and some chatter I've heard on airline pilot forums, the British Airways jetliner crash landing at Heathrow a few months ago isn't a result of engine icing. However, many parts of the online chatter point to the possibility that unusually frigid outside temperatures during flight over the Arcitc region helped cause ice, slush, or some kind of contaminant to build up in the Boeing 777's fuel system, starving both Rolls Royce engines of fuel.
And speaking from experience, if any kind of fuel bowser or if any top-up to the BA038 tanks occurred in China with fuel from a contract services tanker truck, there's always a chance for cross-contamination when the fuel was pumped into the jet's tanks.
1. BBC -- "Engines running on crash plane", 24 January 2008.
2. Andy Pasztor -- "Airline regulators grapple with engine-shutdown peril" on the front page of The Wall Street Journal, 8 April 2008.
3. Previously -- "Two thoughts about short landings"
4. Rendition -- A CIA analyst questions his assignment after witnessing an unorthodox interrogation at a secret detention facility outside the US.