Call or fold to river bet when you are almost sure you are beat?

[MortenB]

Setting: Typical small stakes game online. No specific reads on any player.

Hand: You open-limp with A[img]/images/graemlins/heart.gif[/img] 6[img]/images/graemlins/heart.gif[/img] in the position just before the cut-off. SB calls, BB checks. (3 small bets pot).

Flop is K[img]/images/graemlins/heart.gif[/img] 7[img]/images/graemlins/heart.gif[/img] 5[img]/images/graemlins/heart.gif[/img] giving you the nut flush.
SB bets, BB calls, you call. (3 BB pot)

Turn is K[img]/images/graemlins/club.gif[/img]. SB bets, BB calls, you raise. SB and BB calls. (9BB pot)

River is 5[img]/images/graemlins/diamond.gif[/img]. SB bets, BB folds. (10 BB pot)

Call or fold?

Two possible "solutions" to this:
1:
- Even if you most likely are beind, this is a standard call. You must call 1 BB to potentially win 11 BB, and you cannot with 91% (1/11) certainty put your opponent on a K or 5 for a full house.
- Your opponent can have a lower flush, a pocket pair or be on a pure bluff - in all these cases you will win.
- Folding in this situation is a big error/leak since you could lose a big pot. You only have to win 1 of 11 times to break-even on the call, and in reality you will win much more often.

2:
- This is a marginal and tricky situation, both call and fold could be right, this is read and table dependant.
- Without any reads, a fold is probably better since you are normally more than 91% certain that your opponent has a full house given the action in the hand (particularly since he called the turn-raise, signalling he is not bluffing)
- Many new players tend to wrongly call in these situation with the only argument "it's a big pot". They can get away with this on lower limits, but this can turn into a significant leak on higher limits.

Any input would be helpful. (The hand is simliar to the example on page 150 in SSH)