After experiencing a very discouraging situation, i decided to write a small "guide" to fix the problem.
In the story quest, the secret of the dragon mountain, i couldn't find what to do after beating the ox king.
After killing him, nothing happened , i explored most of the map unsucccessfully.
If this happen to you, follow those steps.
1- Forfeit the quest
2- leave the area
3- log off
4- log in
5- speak again to dog police officer marble at the small camp to get the quest back
6- go back to the time portal
7- walk until you trigger the dialogue and the fight
8- DONT USE ANY ABILITY - This is the important step, if the king dies to fast, goku will never come, the next cinematic will never trigger and you will be stuck.
Killing him slowly will allow the cinematic to start, so you can continue to the next step, finding chichi.
9- At this point, you will notice the Bigfootsaurs dinosaurs appearing on the road, leaving the village. They were not around in the "bugged" version of the quest (only sand lizards).
10- Chichi should be on the ground (on the grass) a bit further away, around the small lake near the destroyed capsul corp houses OUTSIDE the village (where the sky is blue)
When you get close, a new cinematic will trigger.
11- After killing the wave of giant dinosaurs, you should be able to talk to Chichi.
12- You should now atack chichi (for whatever korean reason) and drop her health to around half of the pool.
13- At this point, goku wil leave you stranded in the area to thank you for doing his job, so go back to the Ox king, talk to him and leave the area.
I'd like to thank the player Mightyturtle, who was the only one (on 11 moving players) to answer me, and giving me confirmation that the quest was actualy working on the server, pushing me to find a way around (i was just killing the king too fast with abilities - Rapidshot+ kamehameha)