Tires: Tire Wear-Vibration at high speed, small fortune, car problems

Question
Barry- I'm in a bit of a conundrum, so I would REALLY appreciate your thoughts. I have a Lexus RX335, and have gotten four brand new tires within the last four/five months. The newest tire (the most recently replaced) got a nail in it about a week after I got it; the service station where I bought the tire patched it for me, but ever since then my car vibrates and shakes whenever I go over 70 miles an hour. I took it back to the service station, had them check the tires, and balance them all for free. That didn't change it at all. I've had the allignment redone at NTB, and all the tires balanced there. Nothing has helped, the car still begins to vibrate at 70mph and really shakes as soon as I hit 75-80mph. My lexus has never done this before. I took it to the dealership and they said there was feathering on the tires which was making them "noicy" and causing the vibration, and they could replace the tires for a small fortune. Could it really be the tires? And can I go back to the service station and make them replace the tires for free since they are less than a year old? I appreciate any help/knowledge that I can get--including anything else that might be causing my car problems. I'm about ready to trade it in at this point!!

Answer
Courtney,

Just to be clear

1)  You bought 4 tires - no vibration  Where did you buy them?

2)  One tire had a puncture, so the service station repaired it.  Vibration after that.

Repeated balance doesn't change the vibration.

4 possibilities occur to me:

1)  Is it possible there was a vibration between # 1 and # 2 and you didn't notice it?

2)  Is it possible that the tire was rotated on the rim and now the tire is in a different position relative to the rim and that it is "out of round"?

3)  Is it possible that the service station damaged something on the vehicle during the repair operation and that's what's vibrating?

4)  Is it possible that a particular stretch of highway is causing the vibration?

Anyway, I kind of need to know what think on theser4 possibilities and where you purchased the tires (was it NTB?)