The opera-7.50_alpha1.ebuild has a wrong SRC_URI. It should be changed from SRC_URI="http://snapshot.opera.com/unix/7.50-Preview-1/intel-linux/${PN}-${OPERAVER}.${OPERATYPE}.i386-en.tar.bz2" to SRC_URI="http://snapshot.opera.com/unix/7.50-Preview-1/intel-linux/en/${PN}-${OPERAVER}.${OPERATYPE}.i386-en.tar.bz2"
thx, fixed :)