Hi Folks This sat nav is in a 2008 W211. Its a 2008 model (added to the car as an update from Audio 20)with the latest firmware standard and 2010 maps. Its lost its way several times lately. It behaves ok then suddernly it tells me I'm off road, looses the map picture but the car symbol is still being driven what looks like cross country. The point where it gets scrambled can be on wide open roads where GPS reception would not be affected. It occasionally picks up new roads and provides voice direction but the position bears no relationship with where I am. Assuming the TMC symbol and the five squares in the lower right of the display show GPS reception, the reception can go from no squares to all squares but the system does not recover. The symptoms can last several days then suddernly, map mode with and without navigation directions operates normally. I can change the GPS antenna but other than that I'm lost. Any idea what might cause these symptoms ?