How to enable Aggregation after curl disabled message

I attempted to enable Aggregation (and Aggregation views) without having php_curl enabled. This resulted in an error message saying (something like) the CURL_DISABLED flag is now set. I have now enabled CURL in my php.ini file and restarted Apache, but the Aggregation module cannot be turned on - the checkbox is grayed out.
Presumably the CURL_DISABLED flag needs to be unset? If so, how do I do that? - Thanks