updated, see first post for changelog
that is pretty strange, i don't use proprietary libraries for saving archives, i use standard java libraries, the problem must be with your java virtual machine, first try running the program in admin mode, if it doesn't work try reinstalling (or update) the java virtual machine, also make sure you have enough space in the hard drive where you have mangastreamer it takes around 5/6 mbs for each chapter, if you use auto-save mode it will grow fast in size your archive folder.