Have a 2002 chev malibu v6 front wheel drive, have a howling noise and a vibration when approaching speeds of 100 kph (60 mph), I have replaced both front bearings, rebalanced tires, rotated as well, still no better.. question being, is it possible a bent rim or a broken belt in a tire prevent the wheels from being balanced properly... puzzled?

If it is a tire related howl you are getting as well as the vibration through the steering wheel once you hit about 60 mph there is a number of things you need to do.

1. If you have not had a wheel alignment carried out on the vehicle in the last 6 months then have it done at a reputable suspension specialist (not a tyre dealer). Check your front tires for wear pattern in any event as uneven wear on the tyre is a sure sign of poor alignment. Bad alignment can also contribute to vibration problems. I will guarantee you that when you get the alignment checked it will be out. I am not sure if the rear alignment is adjustable on your model but if it is you will in fact need a 4 wheel alignment. (REFER point 7 also)

2. When the alignment and other necessary front end work is done check to see if the problems persists..

3. I assume your vehicle has the steel rims fitted with the plastic wheel cover. Remove the covers on the front wheels and check for the vibration. If it disappears then the out of balance condition is caused by the covers. (This would not explain the tyre howl though).

4. Remove both front wheels (clean them) and check for damage to the rims on both sides including outside scuffing. (Check tyres also.)
If the steel rim is bent or warped it will not run true and you will get vibration and the tyres will tend to be noisy on the road. It is not always easy to identify a warped steel rim from a visual check. Spinning the wheel on a wheel balance machine should normally show this up though.
If you have alloy wheels fitted these tend to crack and break rather than bend or warp.

5. Out of balance wheels.

It is possible for a wheel to be so badly manufactured that no amount of balancing on a tyre balance machine will fix it. This is a particular problem with cheap alloy wheels but even good quality wheel manufacturers will occasionally let a bad alloy wheel slip past their quality control .

6. Tyres.
If you buy budget tyres you are generally buying poor performance and potentially poorly constructed tyres. Tyres can be produced with inbuilt heavy spots that will make them impossible to properly balance. You will forever have a balance problem (and hence vibration) with such tyres. A good manufacturer will not allow such tyres to slip through quality control. Others are much less fussy. It is always a bad decision to purchase tyres in the lower price ranges.
In your case it is quite possible that if your wheels are ok the tyres are badly constructed and it is not possible to balance them properly. (This would not explain the tyre howl though).

7. Given the age of your vehicle you should have the front suspension and steering components inspected. It is possible that wear in critical components could be the source of the problem. When you take the car to the suspension specialist for the wheel alignment you need to have the front end fully checked over first and any problem areas attended to.

Without test driving and pysically inspecting the vehicle it is not possible to identify the source or sources of the problems. My best estimate is that there are significant wear problems in front end components and that your front end aligment is also out.
However , I hope this helps.

Check the wheel bearings again.....our shop just went through this problem on same type of vehicle.. 3rd set of bearings solved this...we used the " good" ones too (skf) but found out after that the whole batch from manufacturer were defective....hope that helps