Sorry in advance to raise a 'dead' thread, i figured it was better then posting a new one.
I am having this problem as well and like the origanal poster I have trashed preferences, trashed waveform cache etc.
A similar (maybe related??) issue is on some files when I double click the audio to bring it to the veiwer it won't display waveforms, occasionally the viewer will go black completly. Anyone have any advice?
I am running FCP 5.1.4, OS 10.4.9, 4gb ram, on a G5 Dual 2.0. Media (audio included) is stored on Fibre attached storage.