I see things about the critical rebuild.
Apparently the patches from impulse should cover that
The fix has been deployed!
In Impulse, you'll see an update for Neverwinter Nights Diamond. You will also see entries in your games list for Shadows of Undrentide and Hordes of the Underdark. You must also install those two components to enable all Diamond content.
At the end of the Hordes of the Underdark install, you'll see the Kingmaker installer fire off. This is to re-authenticate the premium module content. If you're running Windows Vista 64 bit or Windows 7 64 bit, there is a chance that installer will crash. It's picky like that sometimes. But don't fear! The installer is the KingmakerSetup.exe in your NWN Diamond install folder. Go there, and set the compatibility mode on the installer to Windows 2000 or Windows XP. Once that installer runs, you'll have all of your proper keys and be able to play all premium content!
Enjoy.
I dunno what the impulse installer looks like, but should be a couple updates there, but what I said before sounds suspiciously true. That in order to verify the premium content, it's using a fixed CDKey to register kingmaker.
I am uncertain how to fix the issue, you have to use that CDkey to play kingmaker, so there is no way you and your husband would be able to play that module together (the main modules for game should be fine though). Basically premium conent runs through a verification server based on a CDkey. Kingmaker is premium conent. Both GoG and Impulse do the same thing, they hand out a single key that registers these modules, it uses one key. Thus if you try to play online together you get errors about CDKey in use.
For any other conent you want to play online (IE original campaigns, or downloaded modules), you should be able to play once all your CDKeys are actually set to different values on each computer, which sounds like what you've done.