So, I read in a couple of places that Roger Waters and David Gilmour weren't clickin'. Could someone tell me about this whole thing o,o?
Another thing is, what happened to Syd? I know he had a mental deterioration and had to leave, but what went wrong with him?

The issues between David and Roger are rather well-known. As is what happened to Syd. Too much acid, rumors of a mental illness......either way, he did too many drugs, had a mental breakdown and dropped out of public life until his death.

There are plenty of good books on Pink Floyd. The best one I've read was Nick Masons book called Inside Out.Their falling out is to long-winded to go into detail here.

What about Roger and David?

It's been re-hashed to death here. What possible good could come of dragging that story out again? All it does is cause arguments and flame wars and I doubt the modmins here want that. Again.

But since you just have to know (what Floyd fan worth their salt doesn't know it?)........

David was a passive-aggressive asshole. Roger was an aggressive asshole. Until about 1975 they were able to work together and get sh!t done with a minimum of difficulty. Then Roger started seeing himself as the actual group, with everyone else merely playing the roles of supporting musicians whose job it was to go on stage and make him look good. David naturally, took some offense to that. So they argued. And argued. And argued. Rick got kicked of the band (please do not make me get into that, lest I will piss some people off) and David and Roger argued some more over that too. Finally Roger had enough and left the band. David, Nick and Rick chose to carry on as Pink Floyd, Roger didn't like that. He sued them to try and stop it. He failed. They went on to have two more successful albums and tours......Roger's solo career wasn't as hot. David and Roger to most people's knowledge didn't really speak to one another again until the time of Live 8. Things got increasingly better. They did the Hoping Foundation gig a few months ago, when most people never thought they'd share the same stage again. Now David will be making an appearance to do Comfortably Numb during one of Roger's shows, supposedly here in the States.

I hope that satisfies your curiosity.

That's sad. Thanks.

Could someone else tell me the reason Rick got kicked and who took the decision to do so, supposing there isn't a real leader for the band...

You can read everything here: http://en.wikipedia.org/wiki/Pink_Floyd

Anybody else?

You're not serious.

Go buy Nick Mason's book. He discusses it in detail. You should already own it anyway.