Callanish - Interesting, I've been having similar problems lately and it wasn't until reading your comment that I realized I've been using USB Control more than usual lately as well.

I know that if you exit USB Control after switching to host mode it leaves it in that state. I'm wondering if that's what's causing the battery drain (wild speculation on my part). Perhaps switching back to peripheral before exiting will help (more wild speculation)?

Haven't tested this, just a thought.