Prestashop 1.2.x not showing Categories box

Problem: In the front system (FS) Prestashop is not showing the Categories box. In the back system (BS), clicking on the Catalog tab shows just a blank page, or an error message saying the page is unavailible. The probable reason is that your Home category is missing or messed up. The problem is that you can’t get into the Catalog tab in the backend system to fix it. I ended up in this situation by trying to import categories as a CSV (comma/semi colon separated file) and I had a category in that file with ID = 1. Category ID number 1 is reserved for the Home category. Prestashop did not filter this or issue a warning during the import. So take it from me – do not try to import a category with ID = 1. Solution: I opened my database with phpmyadmin and went to the ps_category table. The row for id_category 1 was messed up and by comparing it to a backup I set it to: id_category = 1, id_parent = 0, level_depth = 0, active = 1. The dates I left as they were. Then I went into the table ps_category_lang and made sure that there were entries for id_category 1 for all languages that I had installed (I had two in my system). Voila, back and front system now works. By adjusting the ID:s in my category import file (making sure no ID was 1) it worked like a charm to import it.