I encountered the same error. QC allows you to create folder with spaces or multiple words with spaces in between. For example "\Folder One\SubFolder Two". However, if you use the import function to load a test into such folder, it will give you the error. If you create a folder directory with no white spaces, then it will work - at least for me anyway. For example, "\Folder_One\SubFolder_Two" or "\FolderOne\SubFolderTwo"
Good luck.