Zawody on really big MySQL tables:
When this happens, the first reaction I hear is “You never told me that MySQL has a 4GB limit! What am I going to do?” Amusingly, I usually do describe the limit when I discuss the possibility of using MySQL with various groups–they often forget or underestimate the impact it will have. Putting that aside, the problem is easily fixed, as that page explains. You simply need to run an ALTER TABLE command.