Dbrepair error

Hi,

When I launch dbrepair on my core server (w2008 R2 SP1), I can see this :

I would like to delete everything under "Computer" because every custom data beneath don't show up in my inventory. (See my first post)

The only data that I can clean without problem is what I have under the first branch "Ordinateur".

For the rest I have an error :

"The object reference is not set to an instance of the object"

What does that mean?

Thanks