Automatic prompt for secure blog admin

Hi,

We are running WP 2.3.3. blog which is attached to the core website on the nav bar. We have a password protected login which is required before a blog admin is allowed to login to the wp admin panel. This has been in place since Feb and has worked fine and provided an additional layer of security.

To read the blog, all you had to do was simply click on the top nav bar link to access the blog and read posts.

However, since Thursday, if you now click on the top nav bar tab to read the blog, you are now prompted for logins for the password protected layer. By clicking ‘cancel’, it removes this panel, but I see from our stats that this is naturally having a very bad impact on the number of readers who actually bother to stay around and read the blog.

Actions and Investigations:
– I am trying to check with all blog users whether anyone has inadvertantly changed anything, but it seems unlikely
– I have checked with the hosting co whether they have done anything but have said no.

Can anyone suggest why this password protected layer is now automatically appearing and how we can rectify?

Many thanks.