Misconfigured network device may render the LAN or WAN unusable. Unfortunately, it's not possible to guess the kind of misconfiguration without prior analysis of network traffic.
Ask your network administrator for help. He will verify the (network-related part of) SPA112 configuration, then he will catch the network packets and will identify the traffic causing disruption. It will help to identify the source of problem.
It's about your priorities. It seems that your outgoing bandwidth is not sufficient for both VoIP audio and "casual networking". With QoS the voice quality has been preferred over other traffic, now the priority is equal so network transfers may distort the voice or broke it at all.
Unless you are ready that the calls may be poor quality or interrupted at all you should use QoS.
If your line is so slow to take current codec requirements you may decide to prefer other audio codec and turn QoS back. Codec requiring less bandwidth will not affect your other network operations as much as current codec, but QoS will maintain your audio undistorted.
Ask your VoIP provider for list of codecs supported.
See Bandwidth consumption page for a codec bandwidth requirement (NEB is the column you are interested in).
I can confirm there is enough bandwith for both (10/1MB), but looks like the router QoS was set so that almost all of it was reserved for just VoIP, thus by just watching a video or downloading anything, broke the network.
Now, since disabling it, i can make calls fine, no distortion or anything and websurf/download/play is fine.
Hope it stays this way, fingers crossed, so i dont have to come back hehe.
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