Hi, I hope someone can help. I had been using Comand APS v4.2 which came with my 2003 W211 E-class with no problems except out of date maps. Then on the forums I read if you upgrade the firmware you can see the ETA on the front screen which I did from the MB dealer. It didn't seem to work with my APS v4.2 so rather than let them charge me lots of diagnostic time I took it away. I borrowed a friends APS v8.0 to see if that would work, and it seemed to work and the TMC came up ok as well. Result I thought. Now and again it would claim to be 'Activating navigation' or 'No DVD in Boot' but on the whole it was sound. After one long journey when it started to play up, I thought I can't do with the hassle, so plugged back in my original v4.2. However now it just says 'No DVD in boot'. If I put in the backup of v8 it sometimes says 'Activation started' then switches to 'No DVD in boot'. I can't understand why it would now stop working. Will the firmwaree upgrades prevent my original v4.2 from working after I ran 8.0 on it ? I can live with slightly out of date maps. Or will it need an original APS v8 to resolve this issue ? Any help appreciated before i fork out for the original v8. I'm very reluctant to take it to Mercedes for diagnostics just yet as they may end up geting me to replace various bits that are not necessary, and land me with a huge bill.