NEW YORK (CNNMoney) -- Verizon Wireless was working to get its 4G network back up and running on Wednesday, following a nationwide outage that began in the early morning hours.
Customers across the country, from California to Ohio to Virginia, took to Verizon's forums to complain that service was knocked out, though gripes were mostly limited to the new 4G LTE data network, which Verizon began to roll out a year ago. Voice calls, texts and 3G data were unaffected, according to the company.
Verizon (VZ, Fortune 500) spokesman Tom Pica confirmed that service returned to normal at around 2 p.m. ET after engineers worked all morning to fix the issue. He did not comment on the cause of the problem.
It was the second nationwide outage in as many weeks for Verizon's 4G network, and the third since April. That's a tough pill to swallow for Verizon, which has built its brand on network reliability.
The bad news for Verizon and its customers is that wireless infrastructure experts expect this isn't the last time the 4G network will go down. Since Verizon was the first company in the world to deploy a 4G LTE network at any great scale, it is dealing with the usual early adopter growing pains.
"Verizon is a pioneer, and it's suffering the fate that all pioneers face," said Ken Rehbehn, analyst at Yankee Group.
Indeed, each new wave of network technology involves some degree of pain. When the last next-generation network (3G) first deployed, it was brought down by widespread capacity constraints that the carriers had not anticipated. Most notably, AT&T's (T, Fortune 500) 3G network became close to unusable in New York and San Francisco following Apple's (AAPL, Fortune 500) launch of the iPhone 3G in 2008.
So what's the trouble with Verizon's 4G network? Verizon isn't saying, and it would be very unusual for a network operator to reveal specifics about why it's having a problem. But experts believe it has to do with the complexities of LTE, which is a much more intricate technology than its predecessors.
Unlike previous systems that use switches to control traffic, 4G uses "cores," that act like large, centralized command-and-control centers. Switches covered city blocks, but 4G cores are now serving multiple states. If one goes out, entire regions could lose service.
Since it's a nationwide event, experts believe all the cores may have been affected by a software or hardware issue.
"This is truly indicative of a larger problem," said Robert Laracuente, vice president of business development at Telenetworks in Puerto Rico. "Best case scenario, some routing isn't programmed as it should be. The worst case scenario is an undetected hardware fault that systemically disrupts the network under certain conditions."
Because this has happened three times now, Laracuente said it would be surprising if Verizon faced a software problem, since the company prides itself on its scrutiny of its engineering. If it is a hardware malfunction, that can be very hard to detect and prevent in the future.
"This is a whole new paradigm of network technology, so I expect that issues will continue to occur," said Akshay Sharma, analyst at Gartner.
Next-generation networks are based end-to-end on Internet Protocol, which routes packets of information over the Internet rather through circuits. That makes 4G about 10 times faster and gives it significantly more capacity for data traffic than 3G, but it also brings a new host of issues to the table.
"IP by its nature is not resilient from day one," Sharma said. "You don't get resiliency and quality of service for free -- you have to engineer that in. That's a new wrinkle that adds to the challenge."
Verizon's 4G customers may have to get used to a few bumps as their first-of-its-kind technology gets all the glitches smoothed out. It's the price pioneers always pay. 
