Just few notes:
We don't know what you mean by "words write just in the oposite direction...". Such description is just too vague. Are you talking about avast! app? Or all apps on your system? Can you post some screenshot?
I don't think that Win32:Malware-gen (as a windows malware) could harm your MacOS X, so I tend to guess the issue "words write just in the oposite direction..." is not related to the presence of Win32:Malware-gen anyway.
Regards,
Mity