From what I remember, the tanks were just one of the problems with the X-33. If memory serves, it was also coming in behind schedule, over weight, over budget, and under performing (fairly typical for a NASA project). If memory serves, the hydrogen tank for the X-33 wasn't cylindrical like the one mentioned in the article. Instead, due to the lifting body design of the vehicle, the tank had an unusual double lobed design that caused all sorts of structural issues in the tank, which also was a major part of the vehicle's structure. In the end, they just couldn't make it work. Here's some more info on the tank failure. It sounds like the X-33 project was just too ambitious with too many unknowns being tested at once. After spending about a billion tax dollars on the X-33 development, Lockheed-Martin declined to spend any of their money to finish it. That suggests something, at least to me.