Currently line 667 of search.php exceeds the php memory limit when imploding the search ids: $search_results = implode(', ', $search_ids); The limit was temporarily increased from 8M to 8.5M, but this was reverted at with the latest php upgrade on dove. We need to sort out the code so that it doesn't exceed the limit (and therefore prevent the page from displaying). We should increase the limit again until I've fixed this (which has just sumped to the top of my TODO list).
*** Bug 146327 has been marked as a duplicate of this bug. ***
Fixed in CVS, it'll be in phpBB-2.0.21-gentoo-p4.