Login 404 on all pages except home page

I installed WordPress 3.0.5 and everything is great, except this login problem that i have.When i am at the home page and click to login, everything works fine, but when im on some other page, after clicking “sign in”, i get 404 error message.

http://www.neum-online.com

Try to go to some other page from menu and try to loggin with some random data, and you will get the error