curl_easy_reset clears all the saved user data, including the CURLOPT_REFERER string.
However, a pointer to this string has been saved in the change.referer field, which is not cleared. This can cause problems if another request is made without the user explicitly resetting CURLOPT_REFERER.
Suggested fix: clear the cached change.referer field (and any other similar fields) when curl_easy_reset is called.
Thanks for the report, this problem is now fixed in the git repository.
To try it out, you either checkout/update your git clone: http://curl.haxx.se/source.html
or you try tomorrow's daily snapshot: http://curl.haxx.se/snapshots/