Well I'm an idiot - the fulltext index on page_text was missing from a default installation. It didn't break searches but probably slowed them down tremendously. Also set engine to MyISAM on page_text to avoid cryptic error messages from MySQL.
// UK lang variables
tinyMCE.addToLang('',{
iespell_desc : 'Run spell checking',
iespell_download : "ieSpell not detected. Click OK to go to download page."
});