incrediBILL - 3:23 am on Jul 20, 2010 (gmt 0)
After all this discussion let me give you a different perspective that I see all the time that most people aren't familiar with.
Just because you see something in Google's WMTs doesn't mean Google found that on your site.
Often scrapers incorrectly parse your page and jumble the URL, happens to me all the time, then Google crawls that page that someone else made with the jumbled URL.
Next thing you know, you have hundreds or even thousands of bogus URLs hitting your site courtesy of Google, Bing, Yahoo, etc. crawling 3rd party idiot sites mucking up WMTs.
So if you can't reproduce the problem, it probably doesn't actually exist, except on sites run by idiot scrapers.