Loosing Wave Forms & Audio Settings - FCP6

Hi Gang

This issue has come up before. When you copy several clips from one project into another, you sometimes get glitchy results: Loss of visual wave forms, loss or interruption in sound levels. Instead of Wave Forms, I see little X's on the audio timeline. Sometimes the Wave Forms reappear only to disappear again. The clips and sequence settings are all the same, no suprises/differences in settings. I've tried: cmd-0 show 'Show Audio Waveforms', no go ...

How have others dealt with this issue?

Thanx

Mike