I've experienced those flashes too back on my old notebook with integrated Intel graphics chip, but I've never figured out what the source was.
A similar problem appears when using
sf::Texture::setSmooth(true) but I guess you didn't use that function.
Since now on my new ATI graphics card I don't experience anything like this, I'd say it's more a hardware problem. May I ask what your PC specs are?
Or did I get your problem all wrong? Maybe a picture of the right and wrong displaying could be helpfull to understand it better.