In the Memory Leak Hotfixes for WPF 3.5 SP1 blog post I mentioned that the memory leak fixes that went into KB981107 were only available for WPF 3.5 SP1. I am now happy to announce that these memory leak fixes are also available for WPF 4. 

You can get the fixes for WPF 4 from here: http://support.microsoft.com/kb/2297328

Enjoy. Jossef