is it loose at the bb interface? if so, the crank arm interface is probably deformed (usually happens from tightening too much or not enough, just like nosebleeds) The only thing to do is get a new crank, otherwise you'll risk your crank arm falling off and a painful crash.
The entire thing, the crown cog and the cranks. The cranks are solidly connected to the cog but the connection between the cog and the bike seems to be faulty. I'll take it in the store this thursday. It's weird because it's a new bike had it for almost 2 months but it happened like 2 weeks after I first got it, now it came back. Thanks for the replies guys.
First off, educate yourself about the parts of your bike. It will really help you in the long run when dealing with a LBS or just talking about bikes in general.
Sounds like it could be that the crank's square taper interface might be rounded out.
I feel like learning the 'correct' or generally accepted terminology will help your case more than anything right now.
At your cranks/bottom bracket.. There are (generally) four main pieces.
The Pedals. These are what you put your feet on, to push down (or pull up if it applies).
The Cranks (crank arms, if you must), which are the lever-arms that the pedals are screwed into. There are two of these.
The Chainring. There are usually either 1, 2, or 3 of these. In this forum, you'll find there is only 1. This is the big ring, attached to (usually) the right Crank Arm. It has teeth. The Chain goes on this. It is most commonly attached by Chainring Bolts (usually 3, 4 or 5).
The Bottom Bracket. This is generally attached to the bicycle frame. It is generally either sealed or looseball, but the spindle is the part that spins. This is also what the cranks are fastened to via bolts in one fashion or another.
Now, this is the basic 3-piece crank design. There is also the 2-Piece crank (which is found on more expensive bikes) and 1-Piece crank, which is the cheapest to manufacture. In this design, the Spindle, and both Cranks are all one solid piece of metal, bent to shape.
Your initial post would lead me to think that the Bottom bracket is not correctly tightened, and it is not an issue of the crank-spindle interface, but more of the bottom-bracket bearings to spindle interface. Your second post is rather difficult to decipher.
Sounds like your BB cups aren't properly tightened. The BB flange on the drive side needs to be pretty tight against the shell in order for the friction to hold it in place. I used to have this problem on my Chesini, though the italian threading on that one makes things worse.
Chances are you need to remove the NDS lock ring, loosen the NDS BB cup (a turn or so), then crank down the drive side flange. Put the NDS lock ring back on. Sometimes it can take a few tries to make sure that there's no play in the spindle, without it being so tight it binds.
If it still gives you trouble you can try a dab of loctite on the drive side threads.