20
how many users do you have, that you're transferring over? looking at the error and the code, it appears that it's unable to convert the registration date data for the users, and i'm guessing you're using a test install of nuke with a test install of xoops?
it's best to try a test install of nuke, but use a duplicate copy of your nuke database, so you have actual data (if this is what you're doing). it really seems that the script is possibly having issues grabbing user data for some reason... hmm...