My Tomtom One was jam, I coun't switched it on by the on/off button. And there is no reset button. What I did, I pried out the speaker cover at the back of the device, it came off verry easily with a small screw driver, I disconected the battery and reconected the battery and Voila!, it is working now. Hope this could help others.
TomTom on the iPhone uses Vocalizer voices (in many languages). I modified these voices to make them work on a PND. This way, besides US English, Spanish and French speaking people, also Dutch, German and Italian speaking people are able to use TTS on their 32MB RAM devices. (The US English, Spanish and French Vocalizer voices are already available for a long time.)
UPDATE 4/11/2013: I have removed all files as they were taken offline ...