Large downloads stall at 100MB

[digitalbitstream]

I've tried several times to work through this issue with support. Our Fusion line reports very good sync stats and always delivers about 5mbps downloads when tested at http://speedtest.sonic.net/ookla/

But large downloads stall out at about 100MB. If restarted they often finish at full speed.
Web pages don't fully load sometimes.
Skype / Google Hangout calls drop.
Gmail reports "can't connect to server".

I've tried two ADSL modems and four different routers, and had similar problems with all, though it is all so inconsistent that I can't be sure of anything. Right now I have an Actiontec GT701D, but in the past it was a Linksys X2000. The router has been a Linksys E1200, a Belkin and also the X2000 and a router running DD-WRT v24-sp2 (03/25/13) mini. Android, Linux Ubuntu 12.04, and OS X Snow Leopard all see the problems. The download stalling at 100MB is fully repeatable on the Mac.

What can I do to track this down?

[jon]

If you have a dynamic wan address, maybe it's Sonic's infamous 5-minute DHCP lease timeout.
Have you tried a static IP?

[digitalbitstream]

I have tried a static IP. But it's a good thought: I have not tried a static with the current setup.

But I'm now reminded of this thread:
viewtopic.php?f=10&t=827

[dave]

Any luck in resolving your issue in the last month? I have a similar issue at my office on Fusion service through a reseller.