I looked for CURLOPT_HTTP_VERSION and found nothing in any of my sites, so I know that isn't it.
I also ran the version of the test code you provided and it gave me an "OK".
For some reason, PayPal is sending out these "urgent" messages but when you try to contact them through a support ticket, they don't have any information. I'm starting to feel like I have to just wait and see what happens June 30th at midnight. (I'm having Y2K flashbacks.) :)