OK, habe das hier in der KnowledgeBase gefunden. Bezieht sich zwar auf R5, aber man weiß ja nie
One customer resolved the issue by installing a Service Pack One from Microsoft that included a revised version of the file Uxtheme.dll. For customers for whom this does not work, the following workaround can be implemented:
1. Disable Themes at the OS level, using these steps:
Control Panel > Display > Themes tab
Change the theme from "Windows XP" to "Windows Classic"
OR
2. Disable Themes for notes.exe, using these steps:
Locate notes.exe in the directory in which Notes is installed (typically C:\Lotus\Notes)
Right-click on notes.exe and select "Properties"
On the Compatibility tab, select "Disable visual themes"
Apply your changes