No, I thought Windows uses the %20 or something similar for spaces... or maybe its only for web addresses? EDIT: The Dakuto Ambition name still stands, so if anyone else has a similar problem - say "This is a case of Dakuto Ambition - use quotation marks!"
Part of the magic (don't know if it did the trick here), apart from proper quoting, is the \\?\ part. Paths starting with that character sequence* access the filesystem directly and bypass APIs. You can do all sorts of evil tricks using that, like creating files or directories with reserved words (CON, AUX etc.) or dotfiles (no name, only extension). It's a trick to remember, for getting rid of invalid file- or dirnames. *must be always complete paths as far as I know, including drive letter