Issue #527 includes some quick and dirty code in a tarball to reproduce the issue, but hasn't been looked at or commented over.
To get an idea of this:
http://www.foxbaltimore.com/versus
http://www.foxbaltimore.com/?PageSpeed=on&Near as I can tell, it's lines like this in shtml that break it:
<!--#include virtual="/inc/header/" -->
Using lines like this instead unbreak it:
<!--#include virtual="/inc/header/index.shtml" -->
Any work-arounds that don't involve modifying several tens of millions of lines of shtml? (We have about 1.5 million files here each ranging between 10 and 80 #include lines, probably half of which are affected)