I bought a nav 6 when i purchased my R1250RT in may of last year. The screen started ghosting after only 6 months. Garmin sent out a brand new replacement but it started having theghosting problem again. Garmin is sending another replacement but a referbed unit this time. Garmins customer service has been easy to work with but being on a 3rd gps in less than 2 years os ridiculous. Are there any non bmw branded gps units compatible with the cradle/mount on the RTs?