Wait, i dont understand... The abs doesnt work until you hit 5 MPH?
If thats the problem, that usually means your ABS Sensors are dead. The're little magnetic strips positioned neer the wheels to record the wheel speed, thus activating your ABS. The sensors must first get some wheel spin before they activate, so the ABS light would be off until you reach about 5 MPH, and since a sensor is broken, your ABS light comes on telling you to get it fixed. This is just one possibility, but ABS isnt really needed unless you drive in alot of snow/ice/blackice or slipery surface. None the less, its a good thing to have, so i suggest going to a mechanic to find out the problem