I have been gettting a "Skyui Error Code 4, Invalid Papyrus.ini settings" every Friday. The documentation says that reloading SKSE fixes the problem, and it does. However I decided to investigate further and discovered the following: If the file Skyrim/Data/Scripts/utility.pex (which is installed by SKSE) has its archive bit ON, the game runs properly. If this file has its archive bit OFF, I get a Skyui Error Code 4. The reason for my getting this error every Friday is because my full backup runs on Thursday night, which turns off all of the archive bits. Simply turning this flag back ON allows the game to run without getting the Skyui error.

I am curious as to why the archive bit would have such an affect. If anyone has any insights on this I would be interested in hearing them.