I have an another attempted fix for this. I know the issue is with Google Docs Viewer and not with my plugin, because I've seen it on other sites that embed the viewer directly, even apart from WordPress. But I haven't nailed down the exact cause.
The file at this link tries to assist by adding a bit of code that may bypass the redirect. I need people willing to test it out and let me know, since I don't have this issue on my installs. The change is minimal and should be safe, but I nonetheless urge you not to try this in a mission critical, production environment. If a problem occurs, you can reinstall the plugin from the repository to the release version.
1. Go to the plugin editor in the WordPress list, and choose Google Doc Embedder.
2. Open up the gviewer.php file for editing.
3. In another window/tab, go to this URL and copy the contents to your clipboard:
http://pastebin.com/e7MrXBji
4. Paste the content over the top of the current content of gviewer.php within WordPress. Save the file.
5. Try your document again and see if the redirect is still present. You may need to clear your browser cache first.
6. Let me know the results!
If someone is unable to follow these instructions and wants a full install via email of the plugin with this patch for testing purposes, please let me know.
Thanks.