Brake Antilock Wheel Speed Sensor problems of the 1998 Oldsmobile Achieva

1998 Oldsmobile Achieva. I own the above mentioned car. I have been having a lot of problems with the brakes, namely the abs system. The abs light continually comes on and my abs makes a funny noise. The brakes also clunk several times when the vehicle is first started. I have taken this to be repaired at substantial cost and I was told that it was the wheel speed sensor that was not working correctly. Well, it was replaced and the problem stopped for a few days. But, has just started again and it is the same thing. The abs light comes on, the brakes get spongy and fail at speeds from 5 mph to 55 mph. The noise from the abs started again and the brakes are clunking again when the vehicle is first started. I can seem to get anybody that is able to do a permanent fix. And I can't get any info from gm about this. I noticed that someone else had filed a compliant on this site about the exact same problem and it was for the same model and year as my car. And, since it presents a clear and present danger, I figured I would file one too.