502 / 400 Error in Apache when using Firebug or ChromePHP
By Frank Forte
It turns out that Apache will return an HTTP error (usually 502) when headers are larger than 8KB. This is much like the White Page Of Death since there is no indication of why the page failed to load.
I developed a fork for ChromePHP that allows you to shrink the ChromePHP debug log so that it prevents the Apache error:
https://github.com/frankforte/chromephp
It shrinks the log by removing notices first, then warnings or errors.