Try this -
When in the live mail program as you look at the folders under your email account you will see an inbox on top. Under the inbox is a folder named Gmail, this folder expands to show "all mail" which is all emails in your box under one folder. Live mail when showing "unread emails" displays the inbox and the "all mail" folder at the same time. This creates the duplicates shown in the unread messages tab. To fix this click on the gmail folder and right click on the "all mail" folder and select Hide this folder.