What browser are you using? I've viewed the forums with IE, Mozlilla and Netscape and never had an issue with either of the 3 at logging in, or viewing forum pages. If you look in the far upper right hand corner near the drop down menu, you'll see a row of buttons. One says login. If it doesn't, snap a screenshot and email it to me here at: firstname.lastname@example.org
so we can see what we need to do further to help you.