[George]

Need Jon's questions answered to try to figure what's happening.

ALSO:
Does the freeze happen when you try to load a song into Keyrite, play it to change key within Keyrite, or play in Keyrite after being changed and saved ? Keyrite is a stand alone program to the extent you can import audio tracks and play them them in Keyrite before or after changing keys, although it isn't meant as a player per se, it will function as one, only one track at a time can be selected to play, no "playlist" options. You do not necessarily need any other program to play a track either before or after keying. Keyrite will play a .WAV file just fine in either the Select Input File or Select Output File section. I frequently use it as a .WAV player.
As Jon pointed out, you would need Microstudio to play a CDG that you've re-keyed the audio portion of.

ALSO:
When you say you've changed MP3 to .WAV, did you do it with conversion software, or try to simply change the file extension. Perhaps this may seem like a dumb question, but have seen some try to simply change the file extension, which works in some applications, but not in this instance.