I have a Dell XPS 15 which shipped with Windows 7 x64, which I recently upgraded to Windows 8. The process went surprisingly smoothly (given that this was an upgrade, not a complete re-install), and the system generally seems very stable.
However, today I noticed that several of the Windows Store apps don't work: they all behave in the same way, launching but then showing a spinning 'wait' animation indefinitely. This is affecting the standard Microsoft Mail, Store, Weather, News, Travel, Finance, Sport, Games and Music apps.
The Bing app just shows a Bing logo on a coloured background (but no wait animation).
The Calendar, Photos and SkyDrive apps open but then show a white screen.
The Maps and Camera apps work without problems.
The live tiles on the Start screen are updating correctly, for example the Mail app's tile shows a summary of new mail despite the Mail app's problems.
All of these applications were working correctly a few days ago. I'm sure I've used several without problems since the last Windows update occurred on 7th November.
Any suggestions on what might have happened and/or how to fix it would be very welcome. I don't need these Windows Store applications, but the fact that they're not working is irritating me.