"We have received a few isolated reports of consoles not working as expected," Microsoft spokeswoman Molly O'Donnell told Reuters in a telephone interview.
Enthusiast Web sites such as Engadget.com and Xbox-scene.com, as well as Microsoft's own Xbox Web forum, carried postings on Wednesday from Xbox 360 owners reporting that some systems had crashed during regular play as well as during online game play using the Xbox Live service.
Problems included screens going black and the appearance of a variety of error messages.
"So, the Xbox 360's been available for, what, 15 minutes, and already the crash reports are streaming in," a poster on Engadget said. The sites did not say how widespread the problem was.
The machine is the first of a new generation of consoles offering high-definition graphics and has been snatched up by game enthusiasts since its launch on Tuesday.
O'Donnell, who declined to say how many reports the company had received, said calls represent a "very, very small fraction" of units sold. The number of calls was not unexpected, she said.
"With any launch of this magnitude, you're bound to see something happening," she said.
O'Donnell said the best way to resolve the issues is to call 1-800-4MY-XBOX for trouble shooting. If that does not solve the problem, she said, Microsoft will repair or replace the unit.