Backend erratic, randomly displays wrong categories, modules etc.

[Ralf Skirr]

I have weird things happening in the admin interface. The data displayed in the admin backend is incorrect and random.

 

Here are a few examples:

 

- The modules page displays the module email notifications as not installed. When I want to install it, it says it's already installed. The module is not working, though.

 

- I can create new categorys. The new category shows up in the database. But they do not show up in the cataloge page in the admin area.

 

- The counts of sub-categories within a category, and the counts of products within a category are displayed wrong. For example, the category list shows 9 sub-categories, but the text says '5 sub-categories in category start'

1. Any idea what might cause such random errors in the admin interface?
   
2. What would you try to fix it?
   

Thanks,

Ralf