Close outlook, Start-> Run; outlook.exe /resetfolders
Failing that, go to control panel > mail. Click outlook profiles then select new and create a new profile with your same credentials.
Change the profile name to always start outlook with your new profile but don't delete the old one. Restart outlook and it should drag everything back down properly from the server. Depending on how much mail you have it may take a few minutes to fully populate.
If it doesn't work you can change back to the old profile and it will be as you left it.