question about concurrent ZK paper by Prabhakaran & Sahai
I'm one of the authors. Someone pointed me to this question. Based on a quick reading, here's an attempt at answering your concern.

What may not be very clear from this version of the description of the simulator (this was the first time I was describing a simulator, and admittedly it reads a bit too much like machine language) is that the view output by the simulator, after all the pushing and popping of the stack, corresponds to only the traversal through edges labeled with L1 and R1. So even if the verifier aborts somewhere else, it just get popped off, and the simulator continues.

I'd recommend the FOCS proceedings version (or a slightly expanded version that is available from my homepage) over this e-print version. In terms of the description in the proceedings version, the simulator's output corresponds to the "main thread" of the simulation, and doesn't include any aborts that may happen in the look-ahead blocks. (Just looking at the paper: see Figure 3 for an illustration.)

Hope that helps.

-Manoj