it's not a bug, that's just the risk you run when using an android device. android is not like your typical os like iphone, blackberry or windows where you can actually close a program. android keeps them all open since it manages apps differently, thus running a higher risk of your phone freezing or rebooting. a stronger processor will result in this happening a lot less of course. it shouldn't happen too often, but i would expect mine to crash every once in a while.