Well, after doing all the recoding I needed to produce binary “correct/incorrect” scores for all the respondents, I ran the IRT model on the 1992 NES, and my computer at work (not exactly shabby – a 1.15 GHz AMD Athlon XP with 1 GB of RAM) ran out of memory when it tried to save the respondent abilities after about 30 minutes of pegging the CPU and eating up my memory and swap. I guess I had more respondents this time than when I did the Dutch model for my dissertation.

The moral of this story: rerun the model with a bit more thinning on my faster AMD64 box at home.

Update: It works much faster (and without killing my computer) when the data matrix is actually set up correctly. Go figure.