My installations of versions 1.4 and 1.51 both blocked upon attempt to invoke the webclient (now 'admin' in 1.51). On attempt to login as i2b2/demouser, I receive the message quoted above. I see in conversations at https://www.i2b2.org/software/augrepo.html that others have encountered this problem, and resolved it by installing curl. I do have php-curl installed, however, and the problem persists.