What you experienced is called 'speed wobbles' and it can happen for numerous reasons with wheel issues being one of them.
Basically it's an oscillation of the front end of your bike that hits resonance at certain wheel speeds. Often rough roads contribute to the onset of speed wobbles as they provide the initial vibrations that then build into full blown trouble. It's a case of an under damped system and it's often hard to pin down the exact cause but contributors include:
- Tight or loose headset
- Tight or loose wheel bearings
- Out of true wheels
- Too much tire pressure for the road conditions
- Too much or too little weight on the front end due to positioning issues
- Very rough roads
- Wind conditions often coupled to deep aero wheels
The only thing you changed was the wheels but that doesn't mean the wheels are at fault, it could be for instance a loose headset or weight distribution issue but your previous wheels or tires dampened the system enough that you didn't have the problems. OTOH, the simple fix is to avoid using those wheels or perhaps to run a bit less pressure up front or perhaps larger tires to better dampen road vibrations. Don't be surprised if it happens at some point with your original wheelset, perhaps at a slightly higher speed or perhaps on a bit rougher road as the fact that it happened at all with recently trued and presumably well adjusted wheels implies the system as a whole is marginally dampened for fast riding conditions.
If it happens, start by trying to shift your weight distribution, ride the drops if you were up on the hoods, rise up to the hoods if you were down in the drops. If you can't get it to go away then try clamping the top tube with both knees to dampen vibrations and try to slow down by sitting high and catching air in your chest before very, very carefully applying the brakes to get down below the speed range that causes problems.
Speed wobbles suck but many very good bikes exhibit the problem in certain situations and there is no definite cure. Your best bet is to make sure all mechanical issues are resolved as in bearing preload adjustments and to think about running a bit larger tires at slightly lower pressures if you ride on rough roads a lot and then perhaps have a bike fitter double check your position with attention to stability at speed.
Good luck,
-Dave
