vibrations... not the good kind

I've got a 2001 Corolla auto... it's a very smooth ride both in city and on the highway (last trip to cali, I was doing 110mph on cruise control... with lexus quality smoothness and silence). Anyway, the only problem I have is when i hit between 68 to 73mph... the steering wheel vibrates like crazy. I don't know if it's just the tires or anything else that may be more serious. As far as the tires go, they've got 80% tread... I'm kinda lost on this one. Any thoughts?

Jae Hoon

Problem with the ECU? Have you tried resetting it? Is this paryticular speed when a gear usually changes?

see if all your tires still have the balance weight attached, they are known to fall off sometimes.