Am I getting this error because I am making a request from a secure site to a non-secure (SSL) location

The short answer is: no.

If you are using HTTP, there is no encryption in the request. So whether or not your process is a site that uses inbound SSL is not a factor. You can turn it off and try it to confirm.

What is really going on? A couple possibilities. You should manually send the request from curl or wget with verbose mode, and also look at the receiving server's logs.

Since you are using HTTP, you can also use telnet, if you are feeling very hands-on.