We are experiencing the same issue that Dan Edgar has posted about before.
That is, when using an ElementHost to host some WPF content in a Windows Forms application ... everything is fine until you run the application on a Windows Vista machine with the Windows Aero theme enabled.
In that case, the screen doesn't refresh, but shows a mangled version of what was on the screen prior to trying to show the WPF content. If you resize the application, then the screen repaints and everything is fine.
We have taken advantage of the workaround that Dan Edgar suggests ... and now it repaints, but there is a considerable pause before doing so. It is ugly.
I wonder if Mark Miller also had this issue. See this post.
We are also experiencing the same problem in a WinForms modal dialog that hosts a WPF ListView using an ElementHost.
We've added the suggested workaround from the Stack Overflow post that Cory mentions above and it seems to resolve the problem, but because of the intermittent nature of the problem, it's very hard to be sure... until we get the next bug report...
Does anyone know if this is a recognised issue with the ElementHost component?