AC 15, 16 selection is really slow!!

[alemanda]

Dear All,
I have a problem with AC 15/16 since I installed them on my machine (DELL T7400 dual quad core + 8GB RAM + Nvidia Quadro FX1700). I kept AC12 and 13 on the same machine.
Working on AC 15/16 selection of objects and entities in the 3D window is really slow specially when I select more item using SHIFT+CLICK. If I click quickly on several items (let's say 10 items in 2 seconds) the last item appears as selected after 3/4 seconds from the last click ...
I installed the latest drivers for the graphic card and I'm using the latest hotfix for both AC15 and 16.
Do some of you face the same problems?
How can I solve this problem?
Thanks to all
Ciao