I was wondering if anyone could help me out with a Skype problem, it's not working for me - I can't send or receive IMs and haven't attempted calls but I'm guessing they won't work either

When I send an IM to somebody the little circle thing just spins around and it says "not sent yet" or whatever and it NEVER sends! I've fixed up Windows 7 firewall settings and everything but it's still not working. Does anyone know why? What connection settings in Skype can I fiddle with to fix this?