I switched it back to use my URI that has a port in it (http://222.222.222:2222), where I receive the Invalid Digital Signature exception, and it worked! However, I hit refresh and BAMO back to giving me the Invalid Digital Signature message. It continues to do so. I'm not sure what happened to get it to work but this could possibly help pinpoint the problem.
Also if it helps, if i use the OAuth Tool it works using the ip with the port (No invalid digital signature error message), but when using the subdomain I have setup, it says Authentication Failed. I moved my code over to another server using a subdomain and it gave me the same response that my ip with the port does (Invalid Digital Signature) exception thrown in my code, but works in OAuth Tool.