Sweater Wizard can work only with .swe files. Firstly, in order to open the files, check if you're trying to open a .swe file with the new version of the program. Right-click the file you want to open, click Properties and check the information next to Type of file. If it is a .swe file, uninstall the program from your computer (Control Panel > Uninstall a program), run CCleaner and install it again. This should fix it.