As we are scrambling to get our application ready for it's end-users, we are starting to notice some troublesome behavior by PresentationHost.exe: it tends to go up to 99% CPU-utilization and refuses to go down again.
Obviously we have noticed PresentationHost going up very fast during our debugging sessions, but what goes up, always does go down again. However, now I'm receiving lots of reports from our end-users that claim the 'application is very slow'. This turns out to be that rogue process, which refuses to go down!!

When we were able to attach windbg to it, we did not find a clear cause. It wasn't executing any of our code, to be sure. But it's definitely busy (no, there aren't any running animations!).

We've also seen multiple instances of the process, where we'd only expect one.

This is turning into a real headache. When we figure it out, I'll be sure to post!