Thank you Nicolas,
I have not solved my problem completely, but I had not imported the User Groups the right way. The lft and rgt were not imported.
But although the database tables are ok now (3000 User Groups), it takes a very long time for User Groups in the Administrator to respond, and longer when selecting User Manager. But when trying to access Global Configuration, it takes even longer, and the screen displays the options as plain text, see screenshot attached.
So... what to do. I have not even imported my articles, my discounts, my users, plus the images, and files to go with them.
What do you think, is Hikashop for shops smaller than mine and should I look elsewhere? I really like Hikashop and the support and all. But if it cannot function with my needs, I need another solution.
If you have any suggestions at all, I will welcome them. I spent so much time, and money too, trying to configure this, I now need a solution that works without any problems.
Thanks.