Xbox 360 users have launched an informal Internet poll in which 16 per cent of respondents said they are having problems with their new gaming console.
Microsoft counters that there are no major bugs and that problems have been reported with only a very small proportion of its machines.
The forum on Teamxbox.com had gathered 496 responses as of Friday morning UK time, with 80 users saying they had found problems with their new Xbox 360 consoles, which went on sale in the US this week.
Claimed problems included unexpected shut-downs during games, system errors and overheating.
One user said his Xbox switched off after 30 to 40 minutes playing "Perfect Dark Zero." He took a break for dinner, restarted the machine and played for 30 minutes before it shut down again. An indicator light on his Xbox had changed to orange, he said.
"I looked in the manual and it looks like it's an overheating problem," he wrote on Teambox.com. "We tried opening a window and putting it beside it. This made little to no difference. Anyways, I woke up in the middle of the night to try it again and it just shut off. Man this sucks."
Others reported having no problems at all: "Bottom line: the jaggies aren't there. It looks beautiful. Controller is awesome. 360 interface rocks."
Another user said his machine ran for six to seven hours "flawlessly."
Microsoft characterised the problems as minor and said there are "no systemic issues" with the Xbox 360.
"We have had a few isolated reports (of problems)," said Claire Dabreo, a spokeswoman with a Microsoft public relations company in the UK.
"Like any major consumer electronics launch it's very complicated and there's always, unfortunately, going to be some percentage that's not going to work perfectly," she said. "But it's an incredibly small fraction and below what you would expect for a launch of this size."