David Eubanks bought two iPhone 3G smartphones a little over a year ago so that he and his college-bound son could share in the iPhone experience. For the most part, they were delighted\u2014until last week. That's when his son upgraded to 3.1 and ran into severe battery problems, Eubanks told me. "My phone, which still has 3.0.1, has had no problems," Eubanks says, adding that he was planning to upgrade but didn't have the time. Now he won't upgrade to 3.1 after watching his son's iPhone slip into what he calls a "coma."Eubanks says his son's iPhone battery life was clearly shorter than his own iPhone after the upgrade. Even worse, when the battery dropped to 50 percent or less, "it refused to receive calls and would not come out of sleep mode," Eubanks says.Apple's support forum lit up with complaints shortly after Apple released iPhone 3.1 a couple of weeks ago. Indeed, my iPhone 3GS showed a noticeable drop in battery life after I upgraded to 3.1. The apparent negative effect on battery life spells trouble for the iPhone, whose battery life has been much maligned even before the iPhone 3.1 release.This ongoing battery problem has prompted Apple to respond quickly, which is somewhat surprising because Apple usually responds slowly, if at all, to most technical problems. Apple technical support representatives reportedly have asked users to install Apple iPhone apps that log power consumption in order to ferret out the cause, as well as fill out a questionnaire about how they use their iPhone. Apple clearly wants to know if iPhone owners heavily use battery sucking apps, such as those running Wi-Fi, Notifications and Location Services."I'd bet that Apple missed some key interactions between the iPhone's software and the processor in the last update that causes it to over-utilize the CPU," Aaron Vronko, CEO of Michigan-based Rapid Repair, an iPhone repair shop, told sister site Computerworld. (Vronko also provided me with tips on how to breathe life into a lifeless iPhone battery.)Eubanks took his son's iPhone to a repair shop in Boerne, Texas. The shop is replacing the battery for $75, Eubanks says. "We are changing the battery just to see if that helps," he says. The repair shop also told Eubanks that "they heard a fix for 3.1 will be coming out in two weeks."Apple's quick response shows just how big of a concern the iPhone battery has become. An already poorly performing battery made worse by Apple's flashy new iPhone 3.1 release is catching the attention of consumers.As one reader weighing the decision to buy an iPhone wrote in an email: "I've heard rumors\u2014or maybe they are actual facts\u2014that 3G phones have short battery lives. I recently went to Best Buy, and a very nice man talked to me about the iPhone. He said I could get six hours of use. Should I worry about the battery life?"Tom Kaneshige is a senior writer at CIO.com? Send him an email at email@example.com. Or follow him on Twitter @kaneshige. Follow everything from CIO.com on Twitter @CIOonline.