I'm having a maddening issue that I'm having trouble finding any information on... A lot of modern style Windows 8 apps are refusing to connect to specific services.
A couple of examples:
MetroTwit - The app opens and offers a "Sign in with a Twitter account" button. Clicking the button shows the app attempting to connect to twitter, then it goes back to the button.
Pulse - A news reading app, asks me to sign in with Facebook, but the button does nothing.
Cumulo - An app designed to connect to various cloud storage providers. It asks me to add services, but clicking any of the options yields no results.
Zipwhip - An app to sync SMS messages with my Android phone. Live tile and notifications work fine. Opening the app shows up-to-date information, but information will not update while I am inside the app.
News Bento - News reading app, works flawlessly. However choosing the option of signing in to Facebook or Google reader does exactly nothing.

At first I thought these may have been issues with the individual apps, but I have more examples than I've listed here, so the problem is widespread. A pattern seems to be emerging which makes it look like a security setting somewhere is messing things up, but I don't know where to look.
Mail, People and Calendars work fine. UAC is enabled. I've also run the app troubleshooter (AppsDiagnostic.diagcab) linked from this Microsoft article with no success. This has been going on for a while now, and I'm anxious to get it solved, because it feels like I'm hitting walls any time I try to use anything in the modern interface.
Any ideas?