Yeah, its probably Cloudflare. In Cloudflare settings, turn off RocketLoader. Or setup a Page Rule for the AdminCP Directory, and make sure there are no Cloudflare Apps running with the AdminCP directory.
In the page rule settings for your cloudflare domain, set the Page Rule like this:
Code:
http://yourdomain.com/admincp/*
And set the CloudFlare Apps for that Page Rule to "
Off".
Also, if you changed the name of your AdminCP, make sure you change the AdminCP Page Rule Directory with the correct name of your AdminCP.
It will take a few minutes to an hour for the Page Rule to be active on your domain.
I had this same exact problem for my vB Forum on Cloudflare. It took me awhile to pinpoint where the problem is coming from. And I found out how exactly to Keep CloudFlare active on my domain, and keep the AdminCP from going in a Redirect Loop. What you are doing, is basically disabling the CloudFlare Apps for
ONLY the AdminCP, and keeping them active on the rest of the site.