If the text on a text terminal looks wrong, the first thing to do is see whether it is wrong in the buffer. Type C-l to redisplay the entire screen. If the screen appears correct after this, the problem was entirely in the previous screen update. (Otherwise, see the following section.)
Display updating problems often result from an incorrect terminfo entry for the terminal you are using. The file etc/TERMS in the Emacs distribution gives the fixes for known problems of this sort. INSTALL contains general advice for these problems in one of its sections. If you seem to be using the right terminfo entry, it is possible that there is a bug in the terminfo entry, or a bug in Emacs that appears for certain terminal types.