The file name, location and malware name help us to help you, e.g. it gives us an idea what it is that we might be dealing with. So can you give the details of the detection for Comodo CCE and Avast rescue disk, the file name, location and malware name given ?
I don't know how it is that you actually get the latest virus definitions for the Avast rescue disk, but the one that comes with it is likely to be a little out of date and if this is a false positive then it may have been corrected, then we are only chasing the comodo cce detection, but in any case the above information help us.