Some 40,000 computers in the U.K."s Department for Work and Pensions (DWP) were unable to access their network last month when an IT technician erroneously installed a software upgrade.

In a statement Monday, the London office of Electronic Data Systems Corp. said the service disruption at the DWP, which lasted four days from Nov. 22 to Nov. 26, was caused by the installation of the software upgrade on machines where it was not scheduled for deployment.

The cause of the problem was found after an internal investigation by EDS and Microsoft Corp. engineers who worked around the clock to resolve the glitch, according to a statement from EDS spokesman Malcolm George. Microsoft and EDS run the DWP"s network as part of a US$3.8 billion IT contract.

EDS said the service disruption didn"t affect benefit systems or the payment of pensions and benefits, although it prevented approximately 40,000 computers from accessing core systems. Most functions were restored early on Nov. 25, with full service restored by the next day.

Several steps have been taken to avoid a recurrence of the problem, according to EDS, including the enhancement of the company"s change management procedures and increased checks by EDS"s senior engineers and management staff when such upgrades are implemented.

The IT failure was the latest in a series of computer system problems experienced by the department. The DWP"s Child Support Agency has been struggling with a $863 million system from EDS that has made payments to only one in eight single parents awaiting them. Since 2001, the DWP has spent around $8.04 billion on various IT projects, including the child support system.