I see. There could be various reasons for this problem. A possible reason could be that the input format is not correct... Maybe you may want to double check this, especially that there is a -2 at the end of each line and that items cannot appear more than once in each itemset.
But if this is not the problem, to investigate further, you may send me the input file and tell me the parameters and algorithm that you have used so that I can reproduce the problem. Then, if there is a bug, I will fix it.