Popular legend has it that the Roman Emperor Nero played the fiddle (a colloquial term for the violin) during the Great Fire of Rome in AD 64. This story has given rise to the idiom "fiddling while Rome burns", which means to occupy oneself with unimportant matters and neglect priorities during a crisis. Authentic Catholics can't understand why he (the Pope) seems to allow the perception that he is fiddling while Rome burns. The Phrase Finder has an article about this expression.
In the cartoon by Chris Riddel from The Observer, Gordon Brown, dressed as a Roman emperor, is fiddling while the City burns. He is surrounded by sheet music with titles such as "Re-Election Blues", "G20 Waltz", "Quantitative Easing Be Bop" and "Unemployment Ragtime"—all very indicative of his current woes.
FOOTNOTE The real Nero committed suicide by driving a dagger into his throat. Let's hope Gordon Brown doesn't come to such a nasty end!