I have no idea if this is an eclipse or jboss tools problem. I already posted this here
http://stackoverflow.com/questions/16821926/where-is-this-repository-prompt-coming-from-in-new-juno-install
but have had no answers. That link contains a screenshot. I have to cancel out several times and is so persistent there is one project I can't even close because every tiem I right click on the darn thing I get prompted for my username and password over and over.
????