Movement and Tumbling
If you move normally through an opponents threatened space, the only way an AoO will stop your movement is if you are tripped.
Therefore, if you tumble through an opponents threatened space, the only way an AoO will stop your movement is if you are tripped.
And, just to keep things clear, you draw the AoO from *leaving* a threatened square, not for entering it.
The Tumble check is not for the movement, its for avoiding the AoO created by the movement. There is no retry, failure indicates you move at half speed and still suffer the AoO.
For tumbling *through* an opponents space:
IMHO, "Failure means you stop before entering the enemy-occupied area and provoke an attack of opportunity from that enemy." means that you end your move. You can take any other actions left to you in the round.