TV is freezing.

The only tv which works properly is the one plugged directly into the receiver.

You mean that you have one U-verse TV receiver (probably the DVR) connected directly to the Gateway (probably by Ethernet) and it doesn't have this issue, but your other U-verse TV receivers that connect wirelessly via the WAP have this issue?

How far from the Gateway is the WAP?

How far from the WAP are the receivers that are not working?

Are you in a standalone home or in an apartment (i.e. do you have neighbors with their own Wi-Fi equipment very close or not)?

Have you recently added anything new to your network?

You are correct in that the tv connected directly to the Gateway works properly but the others freeze.  The Gateway and WAP are about 2 feet apart and the tvs not working are in other rooms - one about 20 feet away and the other about 50 -60 feet away.  I live in a house an have 3 wi-fi boosters - one of which sets next to one of the tvs which isnt working.  This is the set up I've had for 4-5 years and everything has worked just fine until this past week.  I had a power blink (flashed off and then back on) during the night just before all this started.  There was no storm or anything - just a power blink.  

Not exactly sure what is going on here, but I would suggest:

- Unplugging the WAP and both wireless receivers for 30 seconds then plugging in the WAP and the closer of the two receivers.  Does that receiver work okay?  Then plug in the further away?  Now do they work?

- Unplugging the wireless extenders to see if the problem goes away while they are all unplugged.  If so, then try plugging them back in one at a time to see if the problem returns when a particular one of them is plugged in.

Are the Wireless Extenders using wired or wireless backhaul?  If wired, how are they connected to the Gateway?

My 3 boosters are wireless and yes, I did as you've suggested with no change.  It is truly frustrating.  I keep thinking the power "blink" had something to do with it (since that is when this started) and could have done something to the boxes OR that the boxes are going bad.  But I wouldn't think they'd both go bad at the same time although they are several years old.  Again, just frustrating!  I tried to contact the online ATT help Sunday night to no avail too.  My kids have been trying to get me to "cut the cord" and go to streaming and at this point, that's my plan.  It would also save me about $100.00 every month!

The power outage could have caused an old piece of gear to go over the edge.  It sounds like perhaps your WAP needs replacing.  You could call in and tell them you've done all this troubleshooting and you'd like to have WAP replaced; they should be able to ship you one.

Thanks!  I appreciate the advice!  :)