[Nat] I'd suggest a string pass -- on every platform -- to change every '\' to '/' before passing it to boost::filesystem::path. I believe forward slash should work everywhere. I find it plausible that backslash would only work on Windows.
That is what I am doing right now but I started using boost::filesystem::path to get out of that business. This e-mail and any attachment is for authorised use by the intended recipient(s) only. It may contain proprietary material, confidential information and/or be subject to legal privilege. It should not be copied, disclosed to, retained or used by, any other party. If you are not an intended recipient then please promptly delete this e-mail and any attachment and all copies and inform the sender. Thank you.