your post is not clear at all. so you got a trojan a few months ago? after cleaning the pc was working perfectly you said? does that include the internet connection? then you went on to say after that it won't connect to internet. so what do you mean by working "perfectly"???
you need to tell us was the internet connection working right after you clean the trojan, and which trojan was it.
if it didn't and it was a fake av type trojan, try a system restore back to a date before your pc contracted the virus.