10Gbit adapter that works for HP Z800

Hi, friends

I am trying to find a network 10Gbit pcie adapter that works with HP Z800 and has driver for windows 7 and 10. 

The best one I could find is intel adapter X520. The problem is when I install the adapter on Z800 i keep getting error with memory slot 5. "unrecognized memory on slot" and the slot is disabled.

I think it is a conflict the adapter with the memory.

I can install the 10Gbit pcie X520 adapter with Z820, Z840 and other workstations from other brands even older than Z800 with no problem. The problem is only with Z800.

My questions is:

Wich is the a 10Gbit network adapter I can use with Z800 with no problem ?

Does any one know a solution or what is causing the problem with the intel x520 and Z800 ?

Thank you guys