I don't specifically know what the problems are but I have downloaded wifite v2 (r85) directly from code google site,placed it in N900 and chmod' it.It is working excellently and gave me the WEP password within 2 minutes.Where as cleven was unable to do so.It is purely on my test.May be lot of flaws might have creeped in while running cleven by me. The other thing is I tried to install earlier version in my Ubuntu and it gave lot of errors like pyrit and cowpatty.Now they are gone.