I've been using this successfully for a couple months with recent versions of WordPress. I attempted to establish an XML-RPC connection however and could not connect. After ruling out my functions.php file and then deactivating all plugins and turning them back on one at a time I was able to isolate this plugin.
I dug into the ultimate-category-excluder.php file and noticed that there were two additional blank lines after the closing php tag at line 265
note, thanks Kai at Zippy Kid for initially pointing out that there appeared to be an extra line or two on my site that was the tip off to look for php tag issues!