It I have a .txt file as an e-mail attachment, I double click and it opens fine in Notepad++

But if Notepad++ loses focus, I am always prompted with "The file "C:\Documents and Settings\username\Local Settings\Temporary Internet Files\OLK89\file.txt" doesn't exist anymore. Keep this file in editor?" when it gets focus again.

So I click Yes to keep it, but it asks me this same question again when it loses/gains focus. It's quite annoying when you're looking at the file and checking another app at the same time.

Is there any way of disabling this check?