Board Thread:Administrator Noticeboard/@comment-68.97.246.93-20130708042146/@comment-3075738-20130708043314

It sounds like the server is the the wrong version. Are you sure the server is hosting Tekkit Classic; Classic has never gone past minecraft version 1.2.5.

Try deleteing the server files, redownload the Tekkit Classic server launcher, and reinstalling the server files.