5d mk II+580 exII in TTL mode = overexpose

Did I miss something? I've set my 580 exII (on camera) to TTL mode, and then it badly overexposes every shot. If I make it back to eTTL, then it's ok. Why I use TTL? I've read on the internet that eTTL uses preflash to evaluate flash exposure, so without it (that is in TTL mode) flash could be a little bit more powerful. Maybe I got it wrong.

I'm into cake photography (that's personal, my wife makes them), but now just made several attempts- it seems, it may be not enough power from 580 ex and 580 ex II, that's knowing that i've used aperture at f11.

Here some sweets for ya, don't eat me:)))
http://www.flickr.com/photos/migle79

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