Dear Casper,
Using PA/PSA in OM side is different than them in PA.
You know PA/PSA data is related to PA but SAP provides such a data and some more like address an so on in OM also to support companies who would keep this data without implementing PA module. Why you would keep PA/PSA in OM side too?
Anyway, to make sure you have valid combination of PA/PSA have look at your customizing at IMG. Go thru: Enterprise structure > Definition > Human Resource Management > Personnel Areas / Personnel Subareas.
And also control assignment of PA to company code at Enterprise structure > Assignment > Human Resource Management > Assignment of Personnel Area to company Code
Cheers,
Omid