I know what the cause is.And the prompt is exactly right: "A copy of the E-Book appears to be running, but it's window could not be found..."
There is more to the message than that, but I just wanted to give you the jist of it.
The reason it is still running is because it takes a few moments to shut completely down.
If you do the old control alt delete trick you will see it still running under processes.
When this issue happens is when you shut down the ebook and then try to turn it right back on again.
(this is something my customers will do, believe me).
I suppose it is a variant of a share violation type of thing.
But I don't think this is a MicroSoft message.
If it were, the message would speak of an application, rather than an ebook.
After all the ebook IS an exe application, correct?
So I wish Sunil would get in here so we could address this.