Can SAN certificates be used for Device certificates?

I had this problem too and I think what Fabien means is that the usage of the cert has to be both for client AND server. I was signing servers from our AD CA using the webserver template which only sets the usage to be for servers. This didn't work when using them on GTM\LTM's - to get this to work I had to use a template that allows for server and client usage. iQuery works fine now.