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Currently Being ModeratedMar 7, 2013 9:17 AM (in response to iphonetroubles)
Downgrading is not supported. I'd suggest you try restoring the iPhone though iTunes on your computer, particularly if you upgraded it to iOS 6.1.2 directly from your iPhone which doesn't seem to be as reliable as when using iTunes.
If you try restoring from a backup and that doesn't fix the problem, try restoring to factory settings and synching your apps. You'll lose the app data and settings, but if the problem is due to a corrupt cache or settings file, that should cure it.