Your connection is DSL I presume.
Do you have your scout connected? or are you using hub only.
If you are using a Scout, disconnect it and remove the connection from the WALL port of the hub. Run with the hub only.
Is your router wireless and are you using a cordless phone? Sometimes older cordless phones interfer with wireless routers.
Is your internet dropping out as well as the ooma hub, or is it just the ooma hub?
If you could go to http://www.whichvoip.com/voip/speed_test/ppspeed.html
and run a voip test and post the results here, it will help us all analyze your connection.
That's enough for now.
I did not have to change the firewall/port settings on the U-verse gateway at all.
I would follow Wayne's advice and "dumb down" your configuration as much as possible until you determine the cause of your problems. Could be inside wiring line quality, wireless interference, bad router, etc., etc.