NASA has delayed the launch of the shuttle Atlantis for at least three weeks, sending the spacecraft back to the hangar for additional booster inspections.
Shuttle managers made the decision just hours before the countdown was to begin for a lift-off on Friday.
The launch of the space station laboratory, Destiny, is now targeted for no earlier than February 6.
NASA wants more time to inspect electrical cables that connect the shuttle with its two solid-fuel rocket boosters. The work cannot be performed at the launch pad so Atlantis had to be returned to its hangar.
During the last shuttle launch on November 30, an explosive device failed to work during Endeavour's climb to orbit because of a bad electrical connector. A back-up charge separated the left booster two minutes into the flight as planned.
If the backup charge had not worked, the results could have been catastrophic.