Ok, so this is an odd one, and as it has a work around its not a huge issue, but it would be good to get to the bottom of it.
If I load an audio file of any type (wav, aiff, mp3 etc) into the project window everything is fine, however if I drag it down to the composition layers panel I get a crash.
However, if I drag the file to the composition widow (to the right) this does not cause a crash, and now that this has loaded the audio file in question I can drag it freely wherever I like without a crash. However if I import a different audio file and drag it downward to the composition layers panel it crashes again.
I am running cs5.5 upodated to the latest 10.5.1.2 and running Mountain Lion.