It sounds as if the top tension is not engaging. If there was that much lint in the bobbin area, the top thread could have shredded and left lint or a piece of thread stuck between the top tension discs.
Try using a piece of *unwaxed* dental floss to floss between the upper tension discs. (Set upper tension to 0 so the discs are as far apart from each other as possible when you do this.) That should dislodge any piece of thread or lint that is preventing your top thread from being tensioned when you thread the machine.
Also, are you keeping the presser foot lever *up* when you rethread the machine? Upper thread will not be seated correctly between the discs if you try to rethread while the presser foot is down.