I did some brief searching, and it looks like FlexRAID has a variety of access denied issues when applications try to read and write to individual files simultaneously. You can find all sorts of posts from users about being unable to use FlexRAID pools with uTorrent and Windows Media Center TV Recording functionality.
I saw some suggestions for solutions, but a lot of it was along the lines of: save stuff used like this to an external volume for your modifications, and then copy the completed files over to the pool. Which isn't much of a solution, especially in this case.
But, I only spent 5 minutes.
