Just to clarify, my understanding is that Rockbox Utility is complaining that the target name of the installed build (in the rockbox-info.txt file) is different to the target name that has been auto-detected. e.g. the installed build may be labeled "h120", but the new Rockbox Utility is detecting the device as an "iriverh120"
So as others have said, you need to override this the first time you upgrade Rockbox using the new version of Rockbox Utility, and then things will match.