A log entry identifies an error in the computer or other system. Another log entry identifies a symptom associated with the system error. The symptom occurs in timeframe prior to the system error and a variable score is determined for the symptom according to the timeframe, the consistency with which the symptom appears along with the error, and the frequency with which the symptom occurs throughout the system log. A new occurrence of the symptom is identified. Whether the symptom's variable score exceeds a threshold value for the symptom is determined. In response to determining that the symptom's variable score exceeds the threshold value, an alert indicating that the associated system error is probable is displayed.