Albatross: good point but in the latest case (Norway) it was the number 2 tank that went 'pop' (quite spectacularly too - I've seen the photos!)
Busdriver; Albatross has pointed you to the limitation, however the reason for this limitation is that using crossfeed introduces a single point failure mode that could result in a double engine flame out, which is an unacceptable concept in Cat A certification. Bear in mind that crossfeed is referring to the engine fuel supply, not crossfeeding between tanks (as in some types.)