Used to have the Hell Noise on FCP 6 on my Imac OS 10.4 and 10.5. Now its happening again on my 17inch Macbook Pro 10.6.6 with FCP 7.0.3. Its F-ing terrifying!
Its not because of excess luma (have luma filters on), audio sample rate (my clips are 48khz), overheating (my processors are at 55 degrees C), doesnt matter which OS or which version of FC. Apple! get it together! This has been going on for years and its a BIG problem! Gonna lose my hearing!