"We do not yet understand what the problem is. Were still scratching out heads," NASA station flight director Mark Ferring told 10 astronauts and cosmonauts aboard shuttle Endeavour and the station, which are flying in tandem 240 miles (384 kilometers) above Earth.

"It doesnt sound like youre going to get much sleep tonight," station flight engineer Susan Helms said.

"No, and I think you can rest assured that everybody who knows anything about a computer is now at JSC here, and were all working hard on it," Ferring replied.

Crucial to sending commands to station systems and beaming telemetry data on the health of those systems back to Earth, all three of the outposts main command-and-control computers remained crippled Wednesday night.

The joined crews of the shuttle and the station, however, were in no immediate danger. The reason: Other outpost computers were automatically keeping station systems running, and both the complex and its power-producing solar wings remained properly oriented in orbit.

The situation, consequently, is not one likely to prompt the station crew to abandon ship or the visiting shuttle astronauts to depart the outpost earlier than planned.

"I dont think its viewed as a crisis situation," Algate said.

In a worst case, the station crew which includes outpost commander Yuri Usachev and U.S. flight engineer Jim Voss could retreat into the two Russian segments of the 17-story complex.

"The Russian segment is essentially unaffected," Algate said. "You could always just have the crew stay on the Russian side of the station while this problem is resolved."

If, however, the shuttle visit to the station is extended a day or more to give engineers additional time to resolve the computer problem, then the launch of the Soyuz taxi flight potentially could be delayed accordingly.

Said Algate: "Thats something that the mission managers will be dealing with over the next day or so."

The computer shutdown, meanwhile, brought to a standstill plans to test a huge new Canadian robot arm that was mounted to the station earlier this week.

Helms had been planned to limber up the construction crane and grapple its 3,000-pound (1,350-kilogram) launch mount to make sure it can handle a relatively hefty load.

The pallet-like crane carrier then was to be handed to shuttle robot-arm operator Chris Hadfield so it could be stowed in Endeavours cargo bay for a return trip to Earth.

But with no way to send commands to the new station arm, both of those jobs were put off until Thursday at the earliest. Algate said the work would be moved to Friday if the computer problem cant be resolved in a timely manner.

The postponement, meanwhile, prompted the visiting shuttle crew to turn its attention to the unloading an Italian moving van that was temporarily mounted to the station Monday.

The shuttle-borne cargo carrier is filled with several tons of supplies and equipment for the station crew, but the $150 million freighter cannot be tucked back in Endeavours cargo bay unless the station computers are fixed.

The reason: A series of complex latches and bolts now holding the so-called multi-purpose logistics module to the outpost cannot be released unless commands to do so can be sent from the failed station computers.

NASA station flight directors, meanwhile, were clinging to hopes that engineers will be able to come to grips with the computer problem in relatively fast fashion.

"Right now were focused on resolving the problem and getting that done so we can accomplish the rest of this [shuttle] mission," Algate said. "And Im confident that well get this problem fixed within the next day or two at most."

As it stands, the shuttle and its crew remain scheduled to depart the station on Saturday -- the same day that Tito and his cosmonaut colleagues are slated to take off from Baikonur Cosmodrome in Kazakhstan.

Made up of astronauts from the United States, Russia, Canada and Italy, the shuttle crew is still due back here at NASAs Kennedy Space Center at 10 a.m. EDT (14:00 GMT) next Monday.