My 5100 suddenly stopped receiving data and showed 'disconnected' in the GPRS menu. A SIM card fault can be confirmed by checking to see if a SIM ID is shown in the 'About' menu on the SatNav. If not then the SIM is either faulty or has lost connection. A connection can be lost if the terminals have a poor contact which happens over time. So, I carefully opened the device and managed to slide the SIM a few mm's back and forth in the SIM carrier. This broke down the poor contact and hey presto! The GPRS signal was restored. If TT are selling products with lifetime services included, they should at least offer free SIM repairs, or design the device with a simple external slot so customers can remove and clean the SIM card. A good product but yet again let down by TT customer service!!