Why are my brakes locking up on me?

in both cases Antonio and funkybob this is a symptom of a bad abs pump. You may or may not get an abs light as the pump can be working enough to register but not enough to work properly. Hyundia are bad with there abs systems and there traction control . Chevs have a better system but when the stability control starts acting up on them the first place i look is at the abs pump. Hope this helps