Autocomplete fails when "Display query log" is checked

If I check "Display query log" on the Devel module administration page, then create a story or page, the autocomplete never completes in my free-tagging taxomomy field. The little blue spinner just spins and spins forever. I have a standard install of Drupal 5.1 on xampp/windows xp, with these extra modules: Devel, Poormanscron.