manny123 - 1:43 pm on Sep 11, 2012 (gmt 0)
I have noticed an uptick in 404s in GWT as well. In my case, I am using the _trackPageview feature of GA to alias the name of some of my long tail pages like so:
Google is treating these like real URLs when I am just using them as an alias to make my analytics more useful.
Double check the "view source" on some of your pages and make sure that you don't find the offending path somewhere in your HTML.