Other than a large file, I don't know what else could cause this. I've read a long time ago that there was a 'bug' like this in Maya 6.5 and Win XP, but since I use 6.5 and XP and so far have had no problems with the sound or anything, except for when I had a very large file.
C. P. U. Its not a big processor... Its a series of pipes!