XM Satellite Radio restored service after a software glitch knocked out the signal from one of its four satellites and disrupted service to many of the company's 8 million subscribers for about a day.
The problems began around noon Monday, the company said. They initially expected to fix the problem after a few hours but service remained disrupted for about 24 hours.
"The problem occurred during the loading of software to a critical component of our satellite broadcast system, which resulted in a loss of signal from one of our satellites," the company said on its Web site.
It is still not clear exactly how many of XM's customers were affected by the outage. Internet message boards indicated the problem was widespread.
The company apologized to customers in a brief statement Tuesday.
XM customers pay about $13 a month for the service.
XM has four satellites built by Boeing and launched between 2001 and 2006. The first two experienced significant problems and are now regarded as "in-orbit spares," according to the company's annual report.
RBC Capital Markets analyst David Bank said the problem will become an issue for investors if subscribers begin to turn away from the service.
"We'll have to find out exactly what happened, whether it's a systemic problem or just a fluke," Bank said Tuesday morning.
The real concern would be if the problems result in lost subscribers, called "churn" in the industry, Bank said, but it is too early to tell if that will result.
Washington-based XM and competitor Sirius Satellite Radio are in the midst of trying to combine.