I know I could have said "It definitely supports QoS" but doesn't quite carry the same weight (excuse the pun :).
As above I am testing with a DV120 as often as I can get away with...
Can you see the traffic stats on that router for LAN devices?
Can you also throttle devices?
Not historically without SNMP monitoring.
Can you change a setting in the QOS to always leave at least 200K spare of upload and download for HTTP and what ever else?
I wouldn't know have not been in IT for a year now.
I'm not interested in making any such changes until a root cause has been identified.
I will be continuing with the current troubleshooting approach.