Office 2007 - Outlook Today is not showing the graphics properly

Hi

We have a problem with one outlook user account.
In the outlook today view, the summer theme is not showing its embedded 
graphics (like the outlook icon in the upper left of the theme) properly.
It 
seems that the reference graphic files for it, couldn't be found. With
other 
users on the same computer, the problem does not exist.

Here is what we have done so far:

- Recreation of the users profile
- Tests on different computers with the users profile (roaming profile)
- locating the absoulte path for the outlook*.htm files (the theme files)

All of this without success or giving us a hint how to handle this issue.

We are working in a Office 2007 and Exchange 2000 environment (migration
to 
Exchange 2007 is in planning)

We have migrated from Office 2000 directly Office 2007. Since the
migration 
to Outlook 2007 the issue exists.

Is this a known issue or has anyone a clue how to fix this?

Regards,

Tobias