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The device may have been dropped before you owned it, and was waiting for that 3 inch drop to push it over the edge. Sounds like you have done a pretty thorough job of troubleshooting the software, which unfortunately means there is some hardware damage inside the device.
If you are brave and somewhat technically savy, there are instructions in our FAQ section for disassembly, but it may make more sense to call it a loss and replace it. 8800 Disassembly - BlackBerryFAQ