According to the NASA website Teams in Mission Control in Houston are weighing the options with regards to a cooling loop that has had a mechanical failure and space walks are being considered. The loop that was shut down, and since been unable to restart, is one of two cooling loops and the problem seems to be associated with a pump that circulates ammonia. The failed loop is said not to have placed the crew in danger "The space station crew is in no danger and all systems are stable, though operating in a "single string" mode without redundancy. "
Thankfully there are two spare pump modules aboard but they are located on the outside of the IIS and thus the potential for a spacewalk to retrieve the parts.
NASA says "Two of the four main buss switching units are cooled by the failed loop. The units switch and route power to various station systems. Mission Control is evaluating whether the heat generation may be low enough to not require powering off these switching units. With the loss of the cooling loop, several systems have been shut down, including one of two S-band communication circuits, one Global Positioning System circuit, several DC to DC current converters in Tranquility and a set of components that route commands to station equipment. Though two of the four station Control Moment Gyroscopes initially were turned off, the crew installed a jumper cable to regain a third gyro. The gyroscopes maintain the station's attitude in space."
As someone who works in the IT field, I feel much safer when the redundant systems are in place. This is however precisely why you build redundancy into systems and I'm sure NASA is considering all of the potential dangers and making their decision accordingly.
