The issue, which has been the subject of a number of reports on Apple discussion forums, is particularly noticeable after , Apple's remote-controlled media software.
"Access the menus in Front Row, (and) you will get streaks of white lines across your screen," said Mike Stanton Sr., who bought the dual-core Intel iMac and has been experiencing the issue.
Stanton, who owns a Pool and Spa shop in Mandeville, La., said the streaking, which has been called "video tearing," is also present when moving the iCal window around and when using certain functions in iMovie.
An Apple representative said the company is examining the issue.
"Apple is aware of this and is looking into it," Apple said in a statement. "If a customer has any technical issues, they should contact AppleCare."
The Cupertino, Calif.-based company, the first Intel-based Mac, at last month's in San Francisco.
Some users have reported that the problem can be alleviated by setting the machine's display to "thousands of colors" versus the standard millions of colors. Enthusiast site ConsumerMachine has posted some other tips and more information about the issue.
In a research note on Friday, American Technology Research analyst Shaw Wu downplayed the problem and said he doesn't think any kind of recall will be necessary. "We believe the video glitch with Front Row can be easily fixed with a software update," Wu said.
Stanton, meanwhile, said he loves the iMac and the iLife software but is nonetheless returning his new Mac until Apple solves the problem.
"Outside of this issue, the machine is a dream," he said, adding that it is "really fast, very stable, and the screen is great."