i have big problem

my blog is at http://bestloser.co.cc
i have problem every time i click any category like weight loss articles or mange weight loss or last entries i get

Bad Request

Your browser sent a request that this server could not understand.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request. here are some of the urls that give me that

http://bestloser.co.cc/category/httpbestlosercocccategoryweight-loss-articles/

it gives me
Not Found

The requested URL /category/httpbestlosercocccategoryweight-loss-articles/ was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

and all the old posts all links on the side bar when i try to view old posts from admin it gives me the same result

ANY IDEA WHAT IS WRONG AND WHAT TO DO

thanks advanced Morw