When you say Audacity crashes, could you be more specific? When does it crash - on launch, when you’re editing, when you’re recording? What are you doing when it crashes - running an effect, cutting, pasting, moving audio, recording?
Do you really need to have a Creative Live! Cam Optia attached?
That device is not really compatible with OSX. The reason is it pretends to be UVC compliant, but as usual, Creative’s implementation is broken. You will probably only notice that if you use it for more than an hour in one session. It also doesn’t liberate the UVC channel, so it will disrupt other AV programs. And you don’t have to use it to do so. Having it connected is enough to get into trouble.
I wouldn’t touch it with a ten foot pole since it will disrupt communication with your Lexicon Alpha.
The actual crash seems to be something to do with window management. Are you using or have just used an effect when you are editing? Are you zooming in/out or playing audio, causing the window to scroll?
Let us know if disconnecting the webcam makes any difference per Cyrano’s suggestion.