Getting 500 errors on live site - seems to be a memory allocation issue?

[eluser]mattpointblank[/eluser]
Thanks for the tip. I wasn't too keen on upping the memory limits so instead enabled CI's output profiler. One of my queries was taking almost a second to complete (fetching 17,000 rows from a table to populate a dropdown list), so I changed it to an AJAX autocomplete instead which not only fixed the error but improved pageload speed too.