Wildcat,
I am brand new to the dso203 and am still playing around with the system and the instructions in the V5.1 upgrade. I do have a new Ver 2.81 with the new wildcat V5.1 including the new FPGA 1.1 that was in V5.1. I want to make sure that I am testing the exact same thing you are when you get the ADC error. I was wandering if you had a more standardized test that people can do to check this. I was thinking you could have a test using the wave generator in the dso203 and A and B channels connected to it for the test then save the configure file and uploading it to this forum so we could download it, run it then upload a picture to the forum for you to see.
P.S having lots of fum with Version wildcat 5.1. Comparing it to full o-scopes at work. Much better features then the original software in the dso203. Thank for the hard work you have put into it.