Milo's first NL Post... Call or Fold to this River Bet?

[BigBaitsim (milo)]

2/5 NL at Bellagio. Your Hero is in the 10-seat and in the BB with Q4o. Nemesis (SB) has about $1000 in front of him, and is playing a little loose. Hero has about $500.

5 limp to the SB, who calls. Hero raps the table.

Flop is Q28, with two spades (hero has none). SB checks, drunk 1-seat checks without noticing Hero is in the hand, and the entire table checks to the button who bets $15 into the $30 pot. This happens in the three seconds I'm looking at my chips, trying to decide how much to bet (and if to bet). I object, and the dealer tells me it's too late, since there was action behind. SB and I call, as do two others.

Pot is $105. Flop is a non-spade 4, giving me two-pair. SB checks, I bet $50. All fold to button, who calls, as does SB.

Pot is $255. River is the 3[img]/images/graemlins/spade.gif[/img]. SB bets $75...