Hello,
In the FF menu there is a page: Help => Firefox Health Report. This page normally shows some stats about the browser, but having RequestPolicy 1.0.0b3 installed will cause it to display an empty page. I have default block policy enabled. If I disable blocking in the addon options menu the page works fine. If I also disable the lower two subscription options, the page is blank again no matter, if the blocking has been disabled or not. The RP addon has to be disabled from the Firefox extension list in order for it to work again.