backend error showing quantity in multishop

[lpi]

I have a PS 1.6.0.11 (just updated hoping it can solve my problem but nothing changed) 

Actually I have 2 different store configured as multistore.
In backend --> product list a for a lot of products PS show me a quantity, but If I go to quantity panel the total quantity of my combination is wrong. 

I know that the real quantity is the one of quantity panel and the sum of combination.

 

Any suggestion about the problem?

Attached you can find 2 images about the problem.

 

Thanks  in advance, 

L.

Edited February 22, 2015 by lpi (see edit history)