If the save path of a RAR attachment contains a Unicode character, when it is extracted, it extracts into a different folder.
For example if I told it to save RARfile.RAR into "C:\My a(acute) fo(acute)lder" it will actually extract into "C:\My a folder\RARfile" or something similar - note no unicode characters in the final save path.
Note I have substitued the accented characters with (acute) in my example just in case the forum doesn't support them!
I think that folders within the RAR that contain Unicode characters work ok, it's just the same path that get's altered.