Sony says it is addressing technical glitches in some PlayStation 4 gaming consoles, which sold a million units on their first day on sale in North America. Some purchasers have encountered what's been dubbed the "blinking blue light of death" when they attempt to power up their consoles, CNN reported Tuesday. The blue light comes on when a PlayStation 4 is first turned on, but turns to white when the unit is ready for play. Some users have said their consoles are unable to move beyond a constant blue light condition. Some unhappy customers have gone as far as posting one-star reviews on Amazon, although the overall rating is hovering at four out of five stars. Sony has released a detailed troubleshooting guide, suggesting possible problems with the console's power supply, hard drive, related hardware or connection to an incompatible display or television. While acknowledging "a handful of people have reported issues," Sony said the number of affected systems represented less than 0.4 percent of the units shipped, or less than 4,000 out the 1 million sold. "This is within our expectations for a new product introduction, and the vast majority of PS4 feedback has been overwhelmingly positive," the company said in a statement. "We are closely monitoring for additional reports, but we think these are isolated incidents and are on track for a great launch."