About 7,600 Harvard ID cards stopped working around 4:30 a.m. yesterday morning, according to an e-mail from Jeff Neal, a spokesperson for the Faculty of Arts and Sciences.

As a result of the glitch, which Neal said was caused by “a server configuration change earlier that evening,” thousands of Harvard affiliates were unable to access residential dorms and other such Harvard buildings that require swipe access.

According to Cheryl L. Ruane, production manager of Harvard University ID services, Crimson Cash was still accessible while the system was down.

Staff responded to the problem as soon as they were aware of it and began restoring the corrupted data, Neal wrote.

“No data was lost and the integrity of the system was not compromised,” Neal said.

Neal said that it took several hours to restore the system and that the system was not fully operational until yesterday afternoon. Several impacted students reported that their cards worked again by noon.

Generally, students reported that the swipe system failure had minimal impact on their daily routine.

Mario E. Leon, building manager of Pforzheimer House, unlocked several of the House’s exterior doors so that students could enter without an ID.

“I just wanted to make sure all students could get in,” Leon said.

Leon, who received an e-mail from the administration yesterday morning pertaining to the problem with the server, said most of the affected IDs belonged to Harvard staff and people with special IDs, rather than undergraduates.

He also said that the glitch only affected the FAS.

Neal said that the IT staff, which investigated the problem, was not aware of similar system failures in the past.

John Koullias ’11 said that he realized his ID no longer worked yesterday morning after being denied entry to multiple doors of Adams House.

Assuming that only his card was faulty, Koullias tried to go to the HUID office, located in the Holyoke Center.

“I was going to go upstairs to the ID services,” he said. “but when I went to swipe my card it also turned red, so I couldn’t get upstairs.”

Eventually, Koullias spoke with a security guard and learned that it was a system-wide problem.

—Staff writer Hana N. Rouse can be reached at hrouse@college.harvard.edu.