I tried to run Boxcryptor_Portable_Windows_2.1.405.117 on system with russian locale, and got this:
The problem is - the Cyrillic letter C is displayed as two characters [?]?
I tried this on Win8.1 / Win7 / WinXP - same result.
I Just reproduced the issue on Windows 10 and forwarded it to our developers. Thanks for reporting!