More work on Alt-Tab. It looks there is something in the map display that is still holding onto data after an invalidate. This is causing the reset functions to fail.
Looked over more DirectShow samples to find the one that is most adaptable. So far it looks like DrawXCL will work, but it'll take experimentation to make sure.
Spent 90% of the day chasing my tail. But I finally got alt-tab to work. Now any problems associated with it will be considered bugs!