If anyone knows why Camtasia is doing this please let me know. This is the first time I've encountered this kind of issue, where AutoNormalize decides to crank a clip up beyond the point of digital clipping. I should mention that I tried recording the offending tone with varying amounts of silence before and after, and also tried recording multiple tones in a row, and it gives the same clipping behavior. But if I briefly record a pure sinusoid before playing it, then the AutoNormalize acts normally.