You're right, my code was shite. Strange though it seemed to work on some files. The following updated version does everything as intended with the help of os.path.join:

def traverse (targetDir):
    currentDir = targetDir
    dirs = os.listdir(targetDir)
    for entry in dirs:
        if os.path.isdir(os.path.join(currentDir,entry)):
            print("Traversing " + os.path.join(targetDir,entry))
            traverse(os.path.join(targetDir,entry))
        else:
            if os.path.isfile(os.path.join(targetDir,entry)):
                print("Processing" + " " + os.path.join(currentDir,entry))
            else:
                print("Not file: " + entry)
    print("\n")