When Jay Reinke's July 31 paycheck wasn't automatically deposited into his bank account, the 42-year-old painter at Arizona State University, went to the school's human-resources office. A paper check was waiting for him. For $0.00.

Mr. Reinke is one of roughly 3,000 Arizona State employees who have been underpaid or unpaid since the school started using new software from Oracle Corp. to manage its payroll. Others have received paychecks thousands of dollars too high. The payroll problem has caused so much unrest that armed police guarded the university's HR office on several recent paydays.

"When you live paycheck to paycheck," Mr. Reinke notes, "it is tough to survive."

The frustration that comes with switching computer software is a perennial water-cooler complaint especially when, like Arizona State, it involves integrating disparate programs into one system to manage everything from admissions and class registration to finance and HR.

So-called enterprise-resource planning, or ERP, software is notoriously costly and difficult to implement. Hershey Co. and Nike Inc. blamed faulty software for multimillion dollar write-offs in 1999 and 2001. And Hewlett-Packard Co. estimates that it lost $120 million when it couldn't respond to an order backlog caused by its new inventory system in 2004. "No one wanted to use the word ERP. For a while it was taboo," says Lee Geishecker, a vice president at AMR Research.

But, in a way, the confusion at Arizona State was all part of the plan.

The Tempe, Ariz., school has installed its new software using an unconventional if painful approach: Admit from the start that there will be mistakes; then work through the glitches with users' help. Most companies take their time and don't start using a new computer system until they are convinced almost everything works right; then they are caught off guard when mistakes inevitably happen. Often, the delays allow them to expand the project's scope, which adds cost and can further compound problems.