One thing that I've found that may fix this is if the profile is set to use cached exchange mode uncheck that option. Click Next and then Finish. Restart Outlook.
To get to the setting go to Control Panel>Mail>Email Accounts>on the Email tab double click your email profile. Uncheck the 'Use Cached Exchange Mode' box. Next. Finish. Reopen Outlook.
Keep in mind I am guiding you down the road to no more cached exchange mode. If you want to go back to cached exchange mode you will want to rename the .ost file it was using to .old and recheck the box so it will create a new .ost file.
OST file locations:
Windows 7 and Windows Vista
drive:\Documents and Settings\user\Local Settings\Application Data\Microsoft\Outlook