I have same problem I was replacing the flip key case from ( EBAY ) and dropped the dam key and it went into 10 pieces on a black driveway and the transponder is gone I vacuumed swept and looked until my eyes hurt in the hot sun . I have one working key now I have looked at needs wings and remotesandkeys.com Needs wings want $685 I think and remotesandkeys.com want $485. OMG the keys are worth more than the car. Also if you but those cheap Ebay flip keys they do not hold up and need to be glued with epoxy I used contact cement and it popped all apart so just a warning . Now my only option is to tear apart my good key fob to remove the only transponder out and glue to ignition ring to use other cut keys but if I loose the 2nd transponder I am screwed . As time goes buy the Crossfire and many Mercedes are going to the scrap heap over a key issue unless someone can bypass the skreem all together and those who have pristine Crossfires the price will go up on these cars value but these cars can fail as well over time. and since my crossfire is a high mileage weekend driver I bought unloved cheap is not worth investing $700 for a key I read these keys will be discontinued by Mercedes soon and they are remaking them for a short time so they can charge what they want. I am now thinking fo selling this car due to expensive repairs . You would think Mercedes would offer a cheap alternative to those who love these cars. I also own a 2013 Mustang with transponders and I bought aftermarket flip keys like the crossfire and I was able to reprogram aftermarket keys easily with with a few turns of the switch and a few buttons pressed of the remote . I have 2 original Mustang keys and 2 aftermarket keys . Why can we do this on the Crossfire . The value on the Crossfires has plummeted due to the expensive costs to repair it. I hope someone comes up with a fix thanks