The same thing happens me.
I saw this msj for a moment, xoops in php debug mode, when load the page when i had access the first time this day. After, it has not happened or... it is very fast to see it.
Protector 2.52
Xoops 2.0.13.1
Php version 4.3.11
This is a typo.
I'll fix it in next relase.