I get that sometimes, and it's super annoying. I also keep my phone pretty clean, in terms of not having a bunch of crap apps. It usually fixes itself after restarting, but that takes 90 seconds, which isn't exactly convenient.
I know this isn't a fix, but I do love that it's possible to launch the camera by double tapping the power button. It saves a few seconds of using the phones screen interface. You can do this when the phone is locked.
And I take pictures by pressing a volume key, which makes single hand pics easier and less jittery.