That's not very clear... Where are you seeing this blocked? What's generating the request and what is generating the response? There's very few mind-readers or magicians online so you'll have to do a bit of legwork to explain what's happening in your scenario.
But... To try & be helpful. What you are seeing is a server complaining that a request (GET) is being sent with body data included. The HTTP protocol doesn't explicitly forbid that. But it makes no sense to include a body and should be ignored. However it looks like whoever wrote the server you're talking to had other ideas and thought they'd be extra strict.
There's a discussion on stack overflow about this sort of scenario BODY with GET. As with most things where there's ambiguity in the spec there's a bit of an argument over who's right and wrong, but the main thing you should take from this is that there's a disagreement on how the protocol should work at each end and one of them has to give way for things to work properly.
Now, why are you getting a body in the GET? You'd have to ask whoever wrote your client. have you tcpdump'ed the request to verify that there really is a body? And you don't have something in the middle adding it? Like all debugging, it's about what you can prove.
