I tried to use launch4j under Windows in a Hungarian environment. The path names may contain various accented characters. The following path didn't work for me when I reached the windres.exe step:
I had to move the whole launch4j directory into C:\Temp\launch4j to work around this problem.
launch4j simply reported that it cannot find the windres.exe file before the workaround.
(The accented letters were rewritten into their URL-encoded versions, or at least they seemed to.)
I am not sure which launch4j version I use, but the .jar file is exactly 181810 bytes long.