@martius - my thoughts

When a user is using Office 2007 on a Remote Desktop Server(RDS) (with an GPO implemented that deletes the locally created profile at logoff) and customizes the Quick Access Toolbar a file is created with the extension qat. Different qat files are made for every application in the Office 2007 suite that has a Quick Access Toolbar.

These files are saved at this locations:
XP:
C:\Documents and Settings\<username>\Local Settings\Application Data\Microsoft\Office\*.qat
Vista:
C:\Users\<username>\AppData\Local\Microsoft\Office\*.qat

The problem is that when you use Office 2007 on a RDS and implemented Roaming TS profiles which are deleted locally on the RDS at logoff these files are also deleted. Result is that users must re-customize the Quick Access Toolbar every time the logon.

Microsoft has an hotfix and an KB article for this:
http://support.microsoft.com/kb/958062
http://support.microsoft.com/kb/955142

Apply the hotfix when there are no open Office applications and add an Registry GPO preference that updates the user’s registry at logon.

Problem solved!