Hi. All of a sudden the speaker on my 920 has blown out. A few times, when I do the speaker test at the Volume Preferences menu, the sound is okay, but when I increase the volume the voice "crackles", I get a yellow screen with an exclamation mark, and then the unit shuts off. As anyone experienced this. Could restoring the backup help or is this a hardware problem. I contacted TomTom support by email from the company's website but have received no response as of yet. TIA.