When I am using text messaging on the 8300, when I press the letter "u" the menu to send or delete the message comes up. Is there a problem with my phone, or did I accidently assign this as a shortcut key. How can I found out if I did and undo it? Or is this an issue I need to resolve otherwise?
Try a battery pull. With your phone on remove the battery for 30 seconds, then put it back in. If this does not resolve the issue, then I would suspect that you may have gotten the device wet (even damp). Which would cause the keypad to malfunction. In which case you will need to replace the phone. If it is indeed water damaged, you cannot make a warranty claim for it.
