For starters, don't store files you are going to pass to a word processor in your application folder.
In production, the app folder is part of "Program files" which is restricted access (and generally read only) to prevent virus activity, and that may be causing some of your problem.
Instead, copy the file to a "writable" folder, and open it from there. This may help:
Where should I store my data?[
^]
If you are trying to do this in a web environment (and the "VB.NET" tag implies this) then you can't do it at all. In development, it works: because the client and server are the same computer. In production, this opens a new process on the server, not the client and the user can't see it at all! (The web host admin can though - and he is unlikely to be amused...)