Vista - Contacts are Shuffled between Groups at Sign In

I have a question regarding my contacts being shuffled at random between
groups everytime I sign into Messenger, I've run 2 Antivirus Programs
(Symantec and Trend Micro's Online Housecall) and I've not been able to find
a viral link to MSN Messenger. I'm not sure if you've seen this posted
recently or if it's an old issue thats already gotten a response, but I'm
constantly having to reorganize my contacts on sign in and it's becoming a
bit of a pain. I googled the problem and there is someone else who has had
this issue but the forum that he had posted on returned no reply. So any help
on this subject would be appreciated, and if you require more information
just leave a message on this post. Thanks in advance for your assistance.