I'd like to know if any one as an idea about what happend on the planet Dagobha (you know, about the cave being filled with the dark side of the force and all).

I think, Dagobah might really be a dead planet Naboo or something like that, but this isn't very likely.

dou you have any ideas??

hmm interesting, I was thinking the same thing about dagobah.... I really would like to know what happens to Naboo I mean it isn't featured in IV V and VI... strange

Maybe it was blown up by the death star ala Alderan? It is interesting though- I was thinking similar first time I saw Phantom Menace, I thought "WTF? Naboo? Where the hell is that???? it's not mentioned in the origional trilogy, unlike Tattoine or Corosant. Perhaps after the Clone Wars and Yoda flees Corosant coz of whatever happens there- Amidala must see him there at some stage, or Luke goes there at some stage as a very small child- remember when he first goes there he says it feels fimiliar like he's been there before

The "Dagobah is Naboo" theory has been around for a while (check aldera.net), and it has been debunked by the Star Map available in every NJO novel, with an updated one in some of the new AOTC books. If you look, you'll see that Dagobah is pretty far from Naboo, closer to the Sluis Van system. Naboo, on the other hand, is closer to Tatooine. My guess is that Vader or the Emperor levelled Naboo, or it was nearly destroyed by the Clone Wars.

"The whole starfleet couldn't destroy a planet; it'd take a thousand ships with more firepower than I've..." -Han ANH

I think in the EU books in the Thrawn trilogy Luke guesses that Yoda fought and killed a sith/dark jedi of great power there and that it's force 'aura' stayed in the area, creating the visions the cave provides and also masking/cancelling out Yoda's presence in the Force at some later point when the Jedi are being hunted and he returns there to hide.

I guess Dagobah is just a swamp planet with primitive life forms, I don't think anyone caused any kind of devastation - it's just naturally 'swampy'.

I don't think Naboo was destroyed by the Death Star, as it seems pretty obvious that Alderaan was the first planet the superweapon was used on. Think about it... Han Solo's a "galaxy-wise" smuggler, he's been everywhere. If the Death Star had destroyed Naboo, a planet that has been pretty important to the events of the universe, Han wouldn't have said it was impossible for the Empire to destroy Alderaan because he'd have heard about the Death Star.

Another Dagobah theory: Maybe it's Yoda's home world. I've heard Lucas said that Yoda's species will play some part in Episode III. Maybe Yoda's species is wiped out by the Empire because they're a Jedi Race--a people that, in general, is very strong in the Force.