My Rider 400 filled up with water and stopped working the first time it was used in the rain last month. The unit is 5 years old and only occasionally used. I contacted TomTom via email explaining the situation, but advised it is out of warranty so not their problem. On close inspection there is no sealant between the front glass and the casing. Sold as a waterproof GPS so this unit is not fit for purpose and TomTom should be held accountable.