But now, it seems a bug is preventing the tool from showing the crawl source errors. Now, when you click on "diagnostics" and then on "web crawl," and then click on the data within the "link from" column, you will see an error pop up that reads "Our system is currently busy. Please try again in a few minutes." Here is a picture:
A Google Groups thread has confirmed the issue and a Google representative, Susan, said:
Thanks for letting us know; we're looking into it. (FWIW, I'm seeing this in my account too.) :-)
I suspect this bug will be fixed fairly soon.
Forum discussion at Google Groups.