Hmm, I'm unable to reproduce. What kind of issue are you having? In there any translation? Is it all English?
I put the Polish Language.xml in my C:\Users\Rob\AppData\Roaming\StrokesPlus folder and restarted S+, the Polish shows up. I also tried Chinese and while my installation doesn't understand/convert the Chinese characters for actual display, I can see it looks the same as it used to.
I'm using Windows 8 64-bit. You may try using Process Monitor from Microsoft and see if you can see where StrokesPlus.exe is attempting to load the file from, and if there are any file access errors.