Need some help please - links not working

[dvds2000]

My forum was hacked yesterday, have got it going again but there is a problem with all the links on the site.

When you used to go to the main page you got a list of all the forums, now that doesn't work and I just get

vBulletin Message
Invalid Forum specified. If you followed a valid link, please notify the administrator

Using the drop down box is fine, takes you directly to the forum, but using the links on the pages returns the same error.

For example at the top of this page if you click 'vBulletin.org Forum' it takes you to a list of all forums, on mine I get the error above.

Anyone any idea what could be wrong or where I should be looking. I have a couple of skins installed for different styles and does it on all of them.

Many thanks for any help