strange...maybe ur roms been corrupted or something. try goodn64 if u havent already. try resetting the registry files for 1964 and all the plugins (if u need to know how go to www.smiff.clara.net - i dunno about smiffs 1964 section, but if u like use the pj64 instructions to uninstall 1964, but replace the word pj64 with 1964 (and dont delete ur pj64 settings by accident)).
I'd like to dissuade people from recommending regedit to go into their system registry, because it is dangerous for the average user. Please use the uninstall .reg file that comes with your 1964 copy. If that file does not work with windows98, we will make another .reg file.