Password Protection not working

I’m newbie to WordPress, and want to create some password protected pages. Problem is the password protection works in IE but not in Firefox, Google Chrome or Safari. In these browsers once you enter the password you just get sent back to the enter your password page.

I’ve tried changing the theme back to default, disabling all the plugins but nothing seems to make any difference.

Other people seem to have the similar problems on the forum, but none that I can find seem to have been resolved.

Anyone got any ideas? I really need some password protected areas on my site.