According to NASA sources, three External Wireless Instrumentation System Network Control Units (EWIS NCU) have been damaged. Apparently, the damage was deliberate.
The EWIS NCU is a computer designed to store various data on the International Space Station.
Specifically it stores data from accelerometers located aboard truss segements outboard of the Solar Alpha Rotary Joint.
Several wires were found to have been cut in each of three EWIS NCU boxes. One box was slated to fly and another was a spare. A third damaged box was a qualification (non-flight) unit.
The damage was discovered by the company that manufactures these units before they left the factory for delivery to NASA.
At the present time there are no EWIS NCU boxes in orbit aboard the ISS. NASA is working to fix at least one of the boxes such that it can be flown to the ISS aboard STS-118 in August.
NASA, Boeing, and USA are not exactly sure how this damage happened but note that these units do not thave any role in keeping the crew safe.
None the less, NASA is rather concerned by the fact that items slated to go to the ISS appear to have been deliberately damaged by someone.