Alright someone asked me about this earlier and since I really am not sure where to put it its going here.
1. Go to your NWN file and open it.
2. Look for nwnplayer.ini and open that up
3. look for DisablePartyInvitePopup=1
4. Make it DisablePartyInvitePopup=0
This will fix that annoyance of party invites not popping up.