This problem might be in more than just Outlook 2007 but I've only noticed it there;
If I have Desktop Effects running in Ubuntu with Outlook 2007 on the current version of Xover Pro, there seems to be a screen re-draw problem. If you switch the window out and come back to it a lot of the text boxes turn black. Only way to fix it is either restart Outlook or turn off Desktop Effects.
Is this known or not?