I have the same issue.
1. Fresh load on WIN 8 Pro, Metro/Modern apps like News, Mail, Financial, Photos, etc worked for about a day or so, then they won't open. Checked screen resolutoin, UAC, and I am not using any AV outside of Win Defender and Win Firewall.
2.Reloaded, complete reinstall of Win 8 Pro, same results, apps worked about a day or so then the regular Metro/Modern apps won't open.
3. Called MS Support and they suggested a WIN 8 Refresh. Did that (it took quite a while) and no change, same apps won't open.
MS has a problem that seems to be affecting a lot of folks, just not everyone is seems. They make us start with the Metro start page, you would think they would have gotten at least that right for everyone. Anyway, I supposedly will get a call from a level 2 support person tonight, but I am more apt I think to get the solution in Eight Forums someday.