Error: http_build_query()

I’ve just begun receiving this error message when I go to add a new event :-

http_build_query() [function.http-build-query]: Parameter 1 expected to be Array or Object. Incorrect value given in /home/[name removed]/public_html/wp-includes/Requests/Transport/cURL.php on line 508

I’ve seen there have been reports of similar errors in the past but as I haven’t found a recent solution I thought I’d better start a new thread.

Any advice on how to fix this would be much apprecaiated.