I'm assuming this is a version which highlights by reading import/includes, and I think your paths are incorrect, as I keep getting messages similar to this "There was an error accesing the file C:\Program Files\BlitzMax\mod\klepto.mod\minib3d.mod\TPhysik.bmx. Unable to read data." on rebuilding module cache. That should be "minib3d.mod\inc\TPhysik.bmx", as the import is "inc/TPhysik.bmx".
It also only seems to be showing the error on modules that have nested includes.
It also only seems to be showing the error on modules that have nested includes.