I have 1.6.24 running now and same error. I deleted the plug-in and select delete all files, I do notice that when I reinstall my settings are still there (the rackspace connection info). So not sure if I am doing a complete reinstall or not?
I checked that (was unchecked) same thing. I also checked each of the other SSL options individually but same results each time.
I verified the CDN was working on W3 and it is enabled and working. I looked at the PHP info and curl is enabled and no warnings coming from the plug-in.
It does have curl. The site is hosted on azurewebsites. The same site does have W3 Total Cache plug-in which uses Rackspace Cloud Files as the CDN and that works fine, so I think there is no issue with connecting to rackspace. Perhaps W3 Total Cache conflicts with Updraftplus?