I'm curious if this is typical behavior, or if I have something worth troubleshooting... I'm running Outlook 2007 on Windows 7 (Home Premium) using Parallels build 5.0.9370 and a new Parallels Tools install. While viewing a message in the reading pane, if I drag a file attachment to a Finder window, once it is copied, Outlook switches to a (random?) subfolder of my Inbox. This does not happen if I drag the file from a message opened in a separate window. It only happens while using the reading pane in the main Outlook window.
I’m sorry for the troubles you’re having. To solve the problem as quickly as possible I recommend submitting a support ticket with the Parallels team http://www.parallels.com/support/.