The U.S. Copyright Office’s electronic registration system has been down since Friday, costing the office an estimated $650,000 in lost fees and causing headaches for approximately 12,000 customers.

The outage is part of a bigger computer failure at the Library of Congress, the federal agency that oversees the national library, provides Congress with research advice and operates the Copyright Office, a major player in the global digital economy.

Scheduled maintenance on the library’s James Madison Building resulted in buildingwide power outages, officials said. The library’s information technology office is trying to restore the systems, but officials can’t say when service will return.

“This is pretty significant, and we have to do everything to make sure this never happens again,” said U.S. Register of Copyrights Maria Pallante about the computer crisis. “It’s ridiculous.”

The failure of the Copyright Office’s electronic registration system comes five months after a congressional report sharply criticized the IT systems at the Library of Congress. The report cited outdated and inefficient systems and a lack of oversight. That Government Accountability Office report made 31 recommendations, including several that were made in previous reports dating back 20 years.

The report blamed the library’s leadership for failing to address the problems. Weeks later, James H. Billington, who was appointed librarian of Congress by Ronald Reagan in 1987, announced that he will retire at the end of the year.

The library’s problems go beyond its computer systems. The library’s executive team testified before Congress in the spring about the dire need for more storage space for its ­ever-increasing collections. Some books are stored by size, making them difficult to retrieve, while others are stored on the floor and in temporary carts, leading to permanent damage, officials said.

In addition to the Copyright Office’s electronic filing system, some of the services on congress.gov are not working, nor are the Web sites of the National Jukebox and the National Book Festival. The festival, the library’s largest annual event, is Saturday.

“We regret the inconvenience to our users and are working to resolve the problem as quickly as possible while maintaining the integrity of the systems,” library spokeswoman Gayle Osterberg said in an e-mail.

The Copyright Office previously released what Pallante described as “a major report” on its technological needs.

“We need advanced services that match the state of technology that our customers have. We need enterprise infrastructure that is swift and nimble,” Pallante said. “It cannot stay this way. The Copyright Office is too important to the United States.”

The Copyright Office averages 1,500 to 2,000 online registrations a day, so over a six-day shutdown, as many as 12,000 registrations could not be filed online. Pallante said the customers must register their works on paper forms.

The Library of Congress has addressed some of the GAO’s findings, including the hiring of a chief information officer, a post that is required by law but had been vacant. Osterberg said the library will announce the name of the new executive this month.

Pallante has testified repeatedly before Congress about the need to remove her office from the Library of Congress. This computer failure, she said, is a symptom of the bigger problem.

The House Judiciary Committee, which has held a series of hearings about the future of the Copyright Office, is monitoring the breakdown, an aide said, adding that the situation highlights the committee’s concerns that the library isn’t equipped to keep pace with the digital age.