Station commander Fyodor Yurchikin and flight engineer Oleg Kotov rewired the bank of computers to bypass a power outlet that NASA and Russian space officials believe may have caused them to crash on Monday.

The computers, which are German-made and use Russian software, are critical because they keep the $100 billion space station properly positioned for solar power generation and communications.

Long-term failure could force abandonment of the space station, a 16-nation project that has been continuously manned since November 2, 2000.

"In the very beginning, we were a little bit worried about the status of the computers because, you know, this was the first time the whole set of Russian computers crashed at once," Kotov said in a crew press conference from space.

"This morning we finished our trouble-shooting activity and now we have a good set of computers."

The computers will be tested to make sure they are working well enough for the space shuttle Atlantis to leave the station.

It docked with the orbital outpost on June 10 and has been keeping it stable during the computer crash, but is scheduled to depart on Tuesday. It can stay another day if needed.

U.S. astronaut Sunita Williams, who will return to Earth on Atlantis after more than six months on the station, said the computer problems showed that safety in space is not a given.

"We take spaceflight for granted, and it still is pretty darned dangerous," Williams told reporters at Johnson Space Center in Houston. "We're living in an environment that is not really friendly for humans. It's a serious place and we're doing serious business and serious science up here."

Problems with the computer system started as astronauts installed the newest piece of the station's exterior spine, a massive beam that holds a pair of solar wing panels and a rotary joint so the wings can track the sun for power.

So far, the best explanation for the crash is a subtle change in the space environment as the station has grown, said NASA's space station program manager Mike Suffredini.

As the station flies 220 miles (355 km) above Earth, it plows through streams of charged particles which create friction and build up a static voltage charge on the outside.

"As the station gets bigger, this potential continues to grow," Suffredini said. "I think we're going to find system sensitivities as we change the space station."

The U.S. space agency, has 12 more major components to install on the station before it is finished. The work needs to be completed by 2010 when the U.S. shuttles, the only vehicles capable of hauling the large pieces and assembling them in orbit, are retired.

The Atlantis crew already is staying an extra two days to ready the station for the arrival of new laboratories built by Europe and Japan, scheduled for launch in 2008 and 2009.

A fourth spacewalk, scheduled for Sunday, was added after managers decided to have astronauts fix a protruding insulating blanket on one of the shuttle's engine pods.

Engineers were concerned the blanket, which tore free during Atlantis' June 8 launch, could leave the shuttle vulnerable to heat damage during the plunge through the atmosphere prior to landing, currently set for Thursday