If a user has qt4 flag but not X then compilation of vlc fails. As qt4 adds graphical X interface this combination isn't logical. Anyway a small test that stops this madness before compilation is needed. -- to re produce -- USE="-X qt4" emerge =media-video/vlc-1.0.0_rc
Please post your `emerge --info' and attach the log for the failing build.
Reopen this bug when you provide the requested information.