(note: this post applies to TomTom One and ALSO to other TomTom devices)
Some weeks ago I experienced some problems with my beloved TomTom One V2 device: suddenly the device could not receive data from any GPS satellites.
After many tests, I gave up and called the TomTom Hotline.
I had to send my device to Holland for a complete check-up (free of charge): they had to substitute the motherboard!
After that, the TomTom was fine... well, nearly :-(
I could not save my personal settings: "Unable to store settings: File access error".
EVERY TIME I switched-on the device, I had to set-up my country language and other sw preferences.
After some googling I downloaded a TomTom software tool to clean some files from my device: see details in this TomTom technote.
Now everything is fine! Hope it helps somebody ;-)