Add Data Window Broken

Hi all

I'm having a strange problem in ArcMap 10.2.2. I tried to open (an apparently) corrupt DGN. Since then when I open the Add Data dialog nothing comes up. This happens across all MXD's, the "go to default db" button and the "home" button do nothing. I deleted my "normal.mxt" file and still no difference. Has anyone experienced this and know how to fix it. As a workaround now I'm adding data by dragging from the catalog tab but this is painful when running tools.

Thanks in advance