What I noticed on my first play through with my mage, is that my summons usually never appear. What I mean is that despite charging it up and casting it on a valid terrain and distance, my Flame Atronach never appears. Sometimes, it uses my Magicka and STILL the Atronach isn't there. I finally figured out why.
On my second spellsword play through, I was raiding the Lunar base, you know the one at Whiterun. I decided to cast my lowly wolf and what did I notice? Again my Magicka is drained without any appearence. I turned around and I saw it being spawned a good 150 feet away in the Giant Camp. provoking a Mammoth which I battled and WON on level 7, expert level. After that, I got surprised by a Sabre Cat and still managed to survive it.
TL:TR: Does anyone experience buggy Conjuration on the XBOX360 with the 1.2 patch?