http://www.icyphoenix.com/viewtopic.php?f=35&t=476&p=4010#p4010
-----------------------------------
moreteavicar
Mon 23 Oct, 2006 00:47

Re: Blank pages - not memory related
-----------------------------------
Ok, forgot to say what I did to get around this problem. It seems to be related to categoried heirarchy caching system - I disabled caching to includes/def_tree, cleared the generated contents, and the everything could be viewed once more.

The way to disable caching is to open includes/functions_categories_hierarchy.php

Near the top, I commented out: define('CACHE_TREE', true);

(It even tells you that you can do this in the file!)

Whilst it works, its strange that this error occured... I think it might be due to a broken table somewhere, but I cannot get to the bottom of this in db maintenance.