Thanks for the advice. I'm sure that a restore is the way to go. However I don't seem to be able to get it into DFU mode. In other words the following sequence doesn't work:

Turn the iPhone ON
2. CONNECT it to the dock
3. Make sure iTunes is open so you'll know when it enters DFU mode
4. HOLD the Power/Sleep-Wake button AND the Home button for 10 seconds
5. RELEASE only the Power/Sleep-Wake button and continue to hold the Home button
6. WAIT until iTunes recognizes the phone in DFU Restore mode (in Windows a bubble pops up saying it recognized new hardware "DFU Mode" or something to that effect)

When I hold the power & home buttons for 10 secs, the iPhone just turns off.