People keep telling me my site is blocked as a security risk

This is driving me nuts and I can’t sort it out. I’ve had multiple reports that people’s work or private computer is blocking my site–culturebot.net–as a security risk, yet we can find nothing wrong. We’re not identified in any online directory as a threat site and don’t appear to be hacked. I’ve read online that new computer security software sometimes throws this up in response to the Twitter plug in due to the blinded links–does anyone know if this is true or what we can do to resolve this issue?