Usually, this means the waveform picture for that clip is corrupted. It's important to note, though, that a waveform won't be drawn if the audio engine is active. If you hit play right after recording audio, the program will wait until it stops to finish the waveform picture. But, if it's the case that no waveforms ever come up, it's likely the picture cache is corrupted. In this case you can simply delete it. This causes SONAR to re-draw any previously stored waveform pictures for any projects. This is the default location for those files: C:\Cakewalk Projects\Picture Cache