I have just come across a problem in he admin panel while adding categories.

I have a parent category: Boats inside that I have a sub category: Watersports. inside that a sub category: Jetski and then inside that a sub category: One Seater. When the page refreshed after adding the sub category: One Seater it was totally blank.

Also now when i click on categories, I just get a blank page. I know this problem is related to the last sub category i added, because it happened directly after adding it.

The front-end seems to be ok, the categories are showing.

Does anyone know how i can fix this?