Occasionally, customers will experience hard to diagnose problems such has frequent hardware failures, device lockups, product instability, video distortions, low level user static discharge, device-to-device (such as terminal to printer or terminal to serial device) communication problems or other strange hard to debug issues.
Reversed polarity, no ground, hot ground, low voltage or other AC power outlet problem.
If the customer is technically capable, use a volt meter to analyze outlet to make sure outlet is wired properly, voltage levels are correct and ground is functional. If the customer does not have the technical resources to use a volt meter, there are devices which can be purchased at home improvement stores that are designed to detect gross faults on power outlets (not as effective as volt meter). A sample device which is available from The Home Depot as of the date of this document is the Gardner Bender 3-Wire Circuit Analyzer Store SKU# 345238 $4.95