I also have a bigger problem with managing categories in admin.
When adding a category everything seems fine (looged in as admin), and the category is shown in the category tree (in admin/catalog/manage categories).
After logout and login (again same admin account), the category isn’t shown anymore in the tree (in admin/catalog/manage categories), but in the shop front it appears, as well as in the sitemap.
Very strange. Even worse, it is also not displayed when a new product is added and I like to add the product to this newly added category.
Should mention that categrorie that were imported via the oscommerce import extension are working. But new categrories are not ...
Thanks for your hints, hopefully, as this is boring ...