Does anyone know what could possible cause this error?

[Corleone]

When I click on the links at the top of the screen that show the hierarchy, I get this:

Fatal error: ht=08162f24 is already destroyed in zend_hash.c:852 in Unknown on line 0

Fatal error: ht=0833adcc is destroying in zend_hash.c:519 in Unknown on line 0

It also happens when I simply click on a forum. However, if I re-click or re-fresh, it will not happen.

[Mike Sullivan]

That happens with old versions of php (4.0 beta's). If you upgrade your PHP it'll fix it.