Chuck Stephenson stopped by today to take a look at my wing spar. He is an A&P/IA, and he brought a bright light and a magnifying glass to take a close look. After inspecting a a couple of minutes, he seemed convinced that the damage (shown in yesterday's post), was indeed a crack. He said it looked typical of damage that might occur when a plainer blade is dull.
I will be contacting Aircraft Spruce & Supply to see if they can help me get a replacement.