I'd bet that the clip is the culprit, but I'd change the line as suggested above. Any time the line gets tangled, it can break, but the clip is in contact with the line every time you shoot. Like all stamped metal parts, the clip will have one rounded side on it's edge, and one sharp side, with tiny burs. If this is the prob, you can debur it with a small rattail file or some sandpaper. Be careful not to bend the clip out too far, as it may not return to the drum with enough force to hold the line.

Post a pic if you can.