msn messenger multiple groups contacts

I am using Windows Live Messenger 8.1 & having an issue with it. I need an urgent reply to this, with the issue of contacts in the Windows Live Messenger. The issue with the messenger is that when i formatted the computer & installed the fresh installation of messenger & when logged in i got a strange error that my contacts got doubled with duplicates so i deleted the duplicate ones. Then when one of my contact send me the message it gave me again a strange error saying "The following contact is not part of your contact lists, do you want to add it" Even when one from the duplicate are still available on it...!

Can anyone Help on this.......????

Do one thing uninstall the full program & then download it from the main site & then install that fresh version of that windows live messenger.

Check for virus & malware & try to remove all the malware & viruses from your computer. As in you have a fresh install you must not have virus but sometimes there are possibility that you have a corrupt setup of windows live messenger or windows OS itself.

I will recommend you to use Malwarebytes for malware removal & quick heal antivirus for virus removal. Hope this is helpful for you.