Recently came across a situation where an audio file containing narration was imported into CP and all of a sudden the playback in CP revealed clicking noises. Independently the file sounds just fine, in fact it was created in a professional studio so the quality is perfect.
I took the file into Soundbooth, ran a filter to remove clicks, repair file and saved it out ... no luck.
The solution was to open the audio file in Soundbooth, copy and paste into a new file and save it back out with a different file name. Importing into CP was a success the playback didn't reveal any clicking noises.