This is the danger of translating, this very same shit I encountered in the translation of eMule Plus....
Or, we could use the oh so obvious (and our Swedish friend here made me aware of) "Tillat"
It has the meaning, it has the length.
so the suggestion from me will be:
Section: [Dialog.ContactManager]
Original Text: BlockButton=&Blokker / Fjern blokkering
Fixed Text: BlockButton=&Blokker/Tillat
OK?