Well ok,
I bought a Sony FM transmitter (the one that hooks up to the cig. lighter) and everything seemed fine. The day after, I turn on the car (still using the FM transmitter), go do some shopping and when I got back, the engine didn't want to start! It was cranking but couldn't start. I had to wait 1 minute and start it at half-throttle. Now, I linked the problem directly to the transmitter because I never had a problem like that before. I doubt that little thing could have drained the battery so I don't know where to point the finger. I haven't used it again since then, but I'll use it in my bro's car to see if the same thing happens...
Any diagnostic is appreciated...