Please remember to use WikiFormatting, to fill in the Port field, and to Cc the maintainer of that port. Cc'ing yourself is not needed when you are the reporter.
Yes, despite you running as root (or using "sudo"), most of MacPorts does not run as root; it drops privileges to an unprivileged user (the "macports" user).
MacPorts works fine with the versions of Xcode listed on our install page, which includes 4.3 and 4.4.
Please "sudo port clean gnuplot", then try again, then attach the main.log file if it fails again, so that we can see everything that happened.
