So we can blame the software, but how many people reviewed this software before it was purchased? Where was the oversight? This was a global decision that could have easily been caught.
Furthermore, how many people work in the payroll department? What exactly are they doing, besides sending out incorrect paychecks? If they have crappy software, it is their responsibility to work around it. It would be irresponsible for ANY workplace to be so dependent on any software, even the top of the line versions, to just blindly send out checks that are incorrect.
And for all the blaming of the unions, this is strictly a white collar problem. Some cuts should come to the payroll department. They're not doing their jobs.