This is only a guess, though if you also use other SFML-classes that could be a sign of using a slightly incompatible version of compiler to the compiler that SFML was compiled with.
You may like to download another package, if available, but recently there is gcc 4.8 and SFML website got packages for 4.7, so you would have to try recompiling SFML from source or change compiler if thats your problem.