I read that blog on an 800×600 screen, and the "pick-up" link gets wrapped onto the last line of its paragraph. However the assertion pops up when the link is focused, and there is a small "stub" outline on the end of the previous line. The source around the link in question is this: lots of failed <A HREF="http://www.jimloy.com/bowling/spares.htm"> pick-up</A> attempts.
I see the "stub outline" problem if I resize the window such that "pick-up" is the first thing on its line. But I don't see the assertion. I'm using Mac trunk debug. Can you make a reduced testcase for whatever problem(s) you still see?
I tried with a recent debug build and I no longer see the assertion either.