Sounds to me like your analyzer is turned off. By simply single-clicking in the area where the analyzer normally displays, you should be able to turn it back on. Alternatively, you can go into the Winamp Preferences to Options:Visualization, and check to see if it is set to 'Off' there. Your other options are Spectrum analyzer and Ociliscope.
At least, I assume that is what you are talking about. If I'm mistaken, then feel free to clarify.