Candoo, if you try again, and your ESTA is refused a second time, make an appointment with the US Embassy on Grosvenor Square and get a visa instead. That way they'll either tell you why your ESTA was refused, or they'll tell you they are refusing you a visa, or they'll say everything's ok and here's a 2-year visa (be aware that in my early days they first started with a 1-year, then extended that for another 5, and then finally another 10, so you might only get a 1-year visa).
But the good thing about the visa is that you don't apply for an ESTA in that case because a) it doesn't apply to people with visas, and b) they've actually seen you at the embassy and authorised a visa based on that information.
S.