U2 may have ended their year-long tour tastefully in South Africa, with accolades from Nelson Mandela and civilized brunches under the spreading trees, but an Oasis trek is never trouble-free, and their latest was chaotic to the bitter end. It wound up in Mexico in front of 17,000 fans who were highly entertained when Noel Gallagher's amp caught fire during "Supersonic," thinking it was part of the show. But the fireworks didn't stop there: a second amp sparked off the first, shooting flames three feet in the air. Oasis finally stopped the show for 15 minutes while their crew located the problem, firing up the elder Gallagher's back-up system so they could finish the set.