One embodiment of the present invention provides a system that determines the cause of a correctable memory error. First, the system detects a correctable error during an access to a memory location in a main memory by a first processor, wherein the correctable error is detected by error detection and correction circuitry. Next, the system reads tag bits for a cache line associated with the memory location, wherein the tag bits contain address information for the cache line, as well as state information indicating a coherency protocol state for the cache line. The system then tests the memory location by causing the first processor to perform read and write operations to the memory location to produce test results. Finally, the system uses the test results and the tag bits to determine the cause of the correctable error, if possible.