Oddly enough, I'm only getting this when I click on the "questions" tab. I can open links to questions, go to "tags" page, successfully reach the home page by clicking on the logo etc.
I'm using Chrome version 44.0.2403.157 m, Win8 OS. (Reproduced on Firefox 39.0)
Just checked SO, SU & SF, and over 15 other SEs, beta or graduated. This seems to only happen on meta.SE; giving a "Failed to load resource: the server responded with a status of 500 (Internal Server Error)" and redirecting me to this.