[SDPhantom]

First to note, this is an addon error, not a macro one. Understanding that, we need to find out what addon is really causing taint. The error may say it's nUI, but it has been known to blame random addons when the taint is self-generated inside the default UI.

In order to test this, the error needs to reliably be thrown, meaning every time you do a specific set of steps, the error is guaranteed to fire.

If you can get the error to fire consistently, you need to first disable nUI and see if Blizzard was right in blaming it. If it pops up again, you'll need to go through your addons, enabling and disabling groups of them to single out which one is causing the trouble.

Another note, There are at least a couple addons that have modules and dependencies loaded that will refuse to load without them. An example of this is Altoholic that runs off of DataStore and its modules. Be sure to treat these occurrences as a single addon.