I've seen a couple of these myself happen due to malformed markdown links, it's reproducible. To cause it - you take any page above the homepage, and add a special character (!@#$%^&*()) followed by a backslash. It'll throw the rootparent error.
For example, http://www.example.com/news/*/ seems to throw it consistenly in LAMP, though not in a Windows environment for some reason.
Not sure of the etiquette, perhaps I should've created a new thread rather than reanimate one that's over a year old?