You are absolutely right. This problem seems to plaque a lot of Easy c users and there is no mention about it in the instructions with the firmware upgrade. Another thing that seems to be very common is that people think that the firmware upgrade utility in Easy C or RobotC will bring their cortex up to date and that is not the case. The update you used is the one that will be needed to get those white keys talking to each other.
EasyC and ROBOTC always lag behind a little in adding support for the latest master firmware. ROBOTC V4.27 now contains the latest master firmware, EasyC has not been updated yet, neither has ROBOTC V3.xx (and perhaps never will be at this point, idk). I never really understand why these releases cannot be somewhat synchronized or why the master firmware version check is hard coded into the application.
I am having this same problem with the new version that was just released on 2-13-15. What do I need to click on in options to make this error message not occur? We have a tournament this Saturday(2-21) and we want to make sure that we have the correct master code needed to be able to pass inspection. Do we need the newest version released by VEX or do we need the newest version that is built into the easyC software.