A man holds his iPhone 4 in front of a mobile phone store in Tokyo on June 24, 2010. Hundreds of Apple fans braved sweltering humidity to form giant queues in an upscale Tokyo district in a race to be among the first in the world to get their hands on the latest iPhone. AFP PHOTO/Toru YAMANAKA (Photo credit should read TORU YAMANAKA/AFP/Getty Images)
It's the latest glitch to hit the iPhone 4, which went on sale in the U.S. two weeks ago. Last week, Apple acknowledged that holding the phone in a certain way might reduce its wireless performance, and that all iPhones show the wrong signal strength in some situations.
Dallas-based AT&T said Wednesday that a software glitch in network equipment made by Alcatel-Lucent is to blame for limiting the upload speeds of the iPhone 4. AT&T says a fix is in the works.