Error: Access Denied?

[Zempar]

When I start my MTG forge client, it opens a menu that says:
"An error has occured while starting the application.
Access is denied."
My only option to press from there is "ok."

[Pux]

Have you tried running the game as an administrator? Maybe it wants to modify files and doesn't have the rights to do so.

[Zempar]

I tried running as an administrator, and it does the same thing.