Yes, it has happened to me too. I ended sending in the unit, they had to reload the maps and application, sent it back, again hooked it up to my computer and i lost all data on the sd card! The second time, support told me that the SD card may be faulty, so they sent me a new SD card. Needless to say, I will NOT attach my tom tom one to my computer again. Instead, I copied the SD card onto the desk top, then on another removable drive so I have a copy of the critical maps and data. I should also add, the software that came with the unit, the CD, I was able to make up one backup. After i lost all data on the CD card, the program would no restore it. Support told me to "uninstall" the product. When i did this, my new computer crashed! Support suggested i download the latest TomTom Home application and use it. I did, that's when I lost all data on my SD card for the second time. When i uninstalled the newest application, my computer did not crash....I suggest you back up your card directly to your hard drive then store it on a different type removable device, so you have it.