Adding users to a site

Today I was busy on migrating some data using the Tzunami tool, until I got the following error:

SPS2003HandlerException: Principal 'xxx\xxx' cannot be resolved. I was sure about it that the user existed in the SSP and but to be sure, I checked it a second time. And yes: it existed. So i tried to add that user manually to a site, but the user couldnt be added. I stumbled on that problem for about an hour, until i accidentally checked something in the AD:



Account disabled... SIGH!