Hey everyone. Just signed up on this forum. How you all doing? :P

I've been having some trouble with my authentication server.
It's written in PHP and is meant to authenticate users using their vBulletin login id/ password.

My main application is in C# and what it does is request the login page and tries to sign in using the persons ID and password.

it works for about an hour or two, then it just randomly stops working and i have NO IDEA why it does this. I'll post my code for both the C# request and the php part of it.

So the code is below, the C# part works fine, so does the version check (even though it's pretty ghetto)

So take a look and let me know what you think or if you have any pointers on how I could go about making it better let me know!
(I may just write a mysql based one where I have to verify users manually but i dont want to do that )