Pax,
If you only have chords on the chordsheet, it's the style that determines the time signature. The chordsheet does not set it.
That you cannot hear a 4/4 style when loaded and generated, and tracks are not frozen, sounds like you might have an audio file rendering of the style playing along with the new style you load. Right-click on the Audio menu on the top tool bar and see if you can mute it.
Also, did you play around with Performance tracks? Have you loaded a midi file as the starting place for the song? Did you get this file from the internet?
Lastly, change the song to a 4/4 style. Save the song with a new name. Now open that newly named song in Realband. Does it work now?
Regards,
Noel