Car shakes at high speeds

What would make my 95 Buick Park ave shake at high speeds. 4 new tires new alignment, all tires balanced, and re-balanced & rotated.

i had a problem like that once. turned out to be out of round rims. they were bent. tires balanced perfect, but get going down the road, i got shaking like out of balance tires.

We have had some good discussions on this subject for several years, Click Here (http://www.automotiveforums.com/vbulletin/showthread.php?t=952852) to view some previous threads. BTW, doing a search for "vibration" will give you many more opinions & success stories.