This is in an MVC2 project, so I\'m using C# in ASP. This is what I\'m sending to https://api-3t.sandbox.paypal.com/nvp:
VERSION = 65.0
SIGNATURE = AFcWxV21C7fd0
Yeah, I'm getting the same thing. I tested my code on their production URL and it worked just fine.
Given how much they are focused on developers, it's amazing how horrible their API is. I can get points and follow other people on their little social network, x.com, but I CAN'T TELL WHAT THE CURRENT VERSION OF THE API IS!?! (You have to view the source of the webpage and find it embedded in an HTML comment)