Short story - It's a conflict between this brand of modem and your Apple products (doesn't matter whether it's an imac or AEBS as the wireless receiver on the other end). What I did to solve it was to hard wire the mac to the AEBS which in turn is hard wired to the Qwest modem. Due to your personal layout, this may not be a possibility. What you may be able to do, however, is hook the AEBS up to the Qwest modem, then have your mac (assuming it has wireless capabilities) receive the signal from the AEBS.
Without going into a ton of detail, somehow my mac, combined with the Qwest modem, was actually causing the modem to fail sending an authentication signal to the Qwest substation up the road. I was convinced it was a hardware issue with the modem or a problem with the Qwest substation. So was Qwest. The techs from Qwest came out and replaced the modem twice, swapped wires going form my house out to the street, and tried various changes at their substation. No luck.
The techs were baffled. I had a clean line all the way to the substation with one of the lowest noise levels they had ever seen, and it would survive 10 minutes of testing without a single hiccup. But after 15 minutes or so of hard usage, it would fail. And the problem was always a blinking green DSL light, followed by a red light on the DSL spot. A few minutes later, DSL would come back up and everything was good for another 15 minutes.
What's funny is your connection speed is just enough for a SD movie to finish, but not fast enough for an HD movie to finish prior to the time-out. And don't bother with Qwest. Their techs all give you the same tired line - "Never troubleshot with a mac before" or "We don't support macs". Suffice to say, I brought home a Windows laptop from work, pushed my connection as hard as I could for a sustained period, and there was no drop-out. So it's definitely something between the Apple hardware and the 2wire modem. I would see what other modem they might possibly offer. Maybe that will clear things up.
I must apologize. I didn't troubleshoot it much. When I discovered that this was the problem, and the router was right next to the computer, I just hardwired it and forgot about it until today. Hope this helps in some way. Good luck.