I can't say for sure, but it sounds like one of your selected cards has lost its name, which includes the initiative value that the game finds at that point. Check the names by right-clicking on the initiative cards - you'll probably find that one of the names has been blanked out. Replace it with its name followed by the initiative value (always two-digit, so 9 is 09) in parentheses, looking at others for a guide if needed.