My daughter ran into an issue with her 3G iPhone.  After syncing and updating some apps, the phone no longer clicked when locked or unlocked or when selecting an app.  After checking the silent switch, I powered off and on to no avail.

Here’s the fix.  Perform a hard reset.  Not a wipe/restore.  Hold down the Home button and the Power button. Keep holding them even when the slider appears to power off.  The screen will go black, then an Apple logo icon will appear.  Release the buttons and wait PATIENTLY.  The iPhone 3G is going through its full internal reset / reboot process and this could take a couple of minutes.  Once the device is fully booted, little functions that vanished will have reappeared.

No BSOD but there is a pretty sophisticated OS in there that may need a little reset time once in a while.