So twice over the past week I've gotten beaten with AA or KK when I got about 1/2 my stack in preflop. I don't know what to do in these situations when I feel like I'm pretty much pot committed despite getting ugly flops.

1st hand: UB 25/50c NL

Limp UTG w/ AA on table w/ decent action. 5 cllrs to BB who raises to $4.50. This guy's been raising a lot in the last 20-30 hands. Want heads up w/ him so I make it $20 to go. BB just calls.

Flop is Horrible flop. I've got $22 left and BB has me covered. I'm pretty sure he's flopped a set, but he could also be on AK or maybe AQ or a lower PP. He checks to me. I push in w/ 3:1 odds.

Yep, he hit a set of queens.

2nd hand: 25/50c NL....I'm on a definitely tight table and so far have only seen a few flops and not raised PF once. Get KK in EP, I decide to limp playing it very cautiously if no one raises. 4 callers to BB who min raises, I reraise to $3.75, he min raises back to $6.75 (what's this min raise crap), and I reraise again to $17, and he just calls. What should I be putting him on right now? I'm thinking QQ, AK, maybe overplaying JJ or KK also. Why wouldn't one reraise allin w/ AA here? If he did, I might be able to lay down KK at this point. He's got $23 left. Pot's $37.

Flop comes . Check . Check.

Turn is . He bets $6. I know I should've just folded here, but I think he might still be on QQ or remotely JJ and just feeling the situation. More likely is AK, right? Oh well, I feel pot committed at 3:1 and raise....he comes over the top for a few bucks more and shows AA for a set. Some guy at the table says it should've been obvious he had AA...what am I not seeing.

How should I be playing these hands when I get so much in preflop?

Hand 1: You make EVERYTHING alright. He was the one, which makes mistakes. He should fold on your high limp-reraise but he called. On the flop he was just lucky. I would have bet the same like you. This is poker that he flopped a set. Can happen.

Hand 2: With KK vs. AA you have a high probability to lose your whole stack and there is nearly nothing you can do against it. Preflop was okay but when an Ace hits the flop it is very likely that he has at least oine Ace and you should be ready to give it up.

Two unlucky hands, one played good, the other one good until the turn.

I have to admit that it was pretty obvious to me that he had AA in hand #2.

in hand 1 you have to go broke. at those limits folding would be a big mistake and there is enough money out there that you have to protect it. the previous poster who said you will only be called if beat is just wrong. if he thinks AK isnt calling at these limits hes crazy.
like doyle says, if you get half your stack in preflop dont outthink yourself, and if you run into AA vs KK with 50-100bb stack you should not feel basd about loseing it.
thats the way capped buy ins go, there are some hands you cant get away from
matty

You SHOULD play AA differently to how he did (i.e. he gave you perfect odds to hit a set), but against a relatively passive opponent, who re-RE-raises preflop for the minimum amount, he's got AA 9 times out of 10. I must admit it was fairly obvious to me he had AA as well.