Every time someone visits our website where we have the Olimometer displayed, the web server's Apache Error Log fills up with about 40+ lines of debug, related to establishing a secure connection to PayPal.
In doing some research, I stumbled upon this article: http://stackoverflow.com/questions/5345270/headers-are-showing-up-in-apache-error-log-curl-and-paypal/
The error logs shown on that page are exactly what the web server's logs are showing. The answer on that page is to change verbosity of CURL to 0.
So, by editing /plugins/olimometer/olimometer-class.php and changing:
curl_setopt($ch, CURLOPT_VERBOSE,1); to curl_setopt($ch, CURLOPT_VERBOSE,0);
It has solved the problem. I hope this helps someone and perhaps you will consider changing the plugin to fix this (or explain why it needs this verbosity)