1999 Sentra GXE - Suspension problems?

The car is at 55,000 miles which to me is too early to be having suspension troubles. I suspect that before my g/f got the car that it had a bad accident running over a 4 to 5 inch concrete median at high speed. I suspect this because both tires that were on the front eventually blew out with decent tread remaining on the tires as well as one of the rims is bent. Since then these rims were moved to the back and both have new tires. Just recently coming back from a 300 mile trip the car began to shake violently (the feeling of a tire going bad; about to pop a belt). Before it could pop we pulled off the interstate to a gas station. I had my g/f roll the car back and forth at a slow speed to see if any of the tires were wobbling and the right front one was. Seeing as the two fronts that were in the back previously were the old tires from when she'd gotten the car I opted to replace them both for the remaining 110 mile trip home. Luckily a Wal-Mart Auto Center set a speed service record of getting this all done in under 20 minutes at the end of their day. It appeared that the problem was solved until we got back on the interstate or I should say until we got over 40 mph again. The max speed I could go for the rest of the way home was 60 mph without the car's steering wheel shaking too much and the whole car vibrating even more. It seemed strange that it was still doing this, so I stopped and made sure the lugs were tight and they were. Puzzled I got back in the car and went home on cruise control 60 mph. Strangely enough the car seemed to smooth out when even slightly turning towards the LEFT, but the shaking got a lot worse when turning even slightly towards the RIGHT. Every time we'd hit a bump in the road the shaking would get worse and stay that way for a while eventually smoothing out somewhat. I know they balanced the rims because there were new weights on them. PUZZLED - What could this be? Some have suggested a BEARING went bad? Idler arm connected to the steering wheel? Caster/Camber/Axle? Any ideas anybody? Its in the shop now. I'm just trying to get a head start on their feedback. Thanks ahead of time.

check all ur tires, the rims, allignment, rotation/ balancing. if not that then it must be ur cv joints

As it turns out it was Wal-Mart's fault. Apparently they don't know how to balance rims across all Wal-Mart Tire and Lube Express'. The set of tires that we have on the car was put on by two different Wal-Mart TLE's and all 4 (according to my trusted shop elsewhere) were not balanced properly at all. The only thing I can come up with as far as us noticing it all of a sudden being really bad was that we may have thrown a weight while coming home that day. You can bet I'll be going to Wal-Mart looking for reimbursement for what I had to pay to get all 4 rims balanced elsewhere because they didn't do it properly.