I think you'll find that the version of the vBulletin software used by PRRUNE (v. 3.8.7) has been superseded by a new improved version (v. 4.1.3 as at 5th April 2011). The code base underwent a major overhaul commencing from v. 3.8 in August 2008.
Because there is a need for a major overhaul of the code base to keep abreast of other IT changes, the code base changes are being phased in over an extended period... and as such, are still being phased in.
Thus, you are going to find quirky problems such as the missing pages will continue until the current version used by PPRUNE is updated.
However, updating is an intensive operation, with much database work required, and I couldn't be sure that the owners of PPRUNE are willing to indulge in the necessary upgrades whilst the forum still works reasonably well.
On another forum I moderate, the webmaster has been discussing with the mods, the need to upgrade to the latest version very shortly.
He indicated he is very happy with the performance of the latest versions, and the work being put in by the Jelsoft back-room boys...
