Any advice about packet loss?

I have a Wirespeed modem that runs into a Belkin F5D8320-4 (pre-N) wireless router which in turn feeds into a Netgear F5-108P PoE switch. I run three computers on this connection, as well as a VOiP phone and a Skype phone. My upstream internet speed (below) is pretty fast, and I have a great QoS score. My problem is packet loss. The manifestation of this problem is intermittent sound on VOiP, in about a 1-second repeating cycle. Conversation is impossible. Plugging the computer directly into the modem, avoiding the router and PoE swith eliminates the packet loss problem, but both my Skype wireless G phone and VOiP phone need these pieces of equipment, so eliminating them is not an option. I have updated the router's firmware without any noticable change. Also, in a conversation with Belkin techs, I allocated the wireless channel, also without any obvious effect. My ISP has told me that I am running at 90-100% line capacity, which I according to them and in the tests we went through, I should not be. They are contacting ATT, my DSL line provider, to test. Could this be affecting my packet loss? I am considering the purchase of low interference Cat 6 cables, or possibly starting afresh with a new router. Does anybody have any suggestions before I purchase a new router - and recommendations for a good VOiP router if I do? All advice gratefully received. Speed test statistics --------------------- Download speed: 3523552 bps Upload speed: 661032 bps Quality of service: 99 % Download test type: socket Upload test type: socket Maximum download pause: 36 ms Average download pause: 3 ms Minimum round trip time to server: 106 ms Average round trip time to server: 267 ms VoIP test statistics -------------------- Jitter: you --> server: 0.3 ms Jitter: server --> you: off Packet loss: you --> server: 60.9 % Packet loss: server --> you: off Packet discards: 0.0 % Packets out of order: 0.0 % Number of supported VoIP lines: 11 Estimated MOS score: 3.5