a nl tournament hand ...

[dr_mabuse]

hi folks,

i like to get some advice of a no limit holdem tournament hand recently played:

it is at the start of a large tournament, about 500 people in and each has a stack of about 250 units with small blind 1 unit big blind 2 units.
i am dealt Q [img]/images/graemlins/club.gif[/img] Q [img]/images/graemlins/spade.gif[/img] sitting in the big blind of a full table. UTG + 5 raises 6 units to 8 units.
i decide to reraise further 6 units, he calls.
anyone else folds leaving 2 players 29 units in the pot.
flop: 5 [img]/images/graemlins/spade.gif[/img] J [img]/images/graemlins/spade.gif[/img] 7 [img]/images/graemlins/diamond.gif[/img]
it is checked to me and i decide to put in a full size raise of 30 units and i am called.
up to now i am thinking that i am most likely against a medium pair or 2 very big cards, eventually a pair of K, but i thought i would be most likely reraised pre-flop with KK or AA ?
turn: J [img]/images/graemlins/diamond.gif[/img]
it is checked to me and i decided to bet another 30 units and i am now raised 30 units more.
now i am wondering what is going on ? should i drop here ?
am i against a small set, a set of jacks, quad jacks or KK, AA ?
i decided to call.
river: A [img]/images/graemlins/heart.gif[/img]
the player bet 52 units now.
drop, call ?
i called, but i think i should have folded at least here ?
what hand has the opponent ?
any suggestions on the play of the hand ?

thanks and bye
olaf