Hi,
This is not instant version, this is probably the name of VC. Go to maintenance and see what is mentioned after firmware or OS. it should be something like 6.5.4 etc
Hope i can shed some light on how instant.arubanetworks.com resolves
1) for instant.arubanetworks.com to resolve, client MUST send a DNS request to this url (DNS response is not required for interception)
2) for client to send the dns request, following 2 conditions must be met
a) if DNS server is in the same subnet as the client device, it should be 100% reachable (means it should response to arp request)
b) if DNS server is in another subnet, it doesnt matter if its alive or not coz client will send the request anyway, and instant will intercept and respond with its own IP
In your case, i believe there has to be DNS issue. The best way to find out, is to install wireshark and see what is happening to the DNS request.
Also i am assuming your local host cache doesnt have any static entry for instant.arubanetworks.com