An AOL spokesman declined to say how many accounts had been affected, and also declined to elaborate on the problem beyond describing it as an "equipment glitch." He said the problem was unrelated to a switch failure on 27 March which also brought down AOL Instant Messenger for a short while. AOL IM users with older versions of the free software continued to have problems for days afterward.
A source at the company, however, speculated that unusual solar flare activity could have caused the disruption. Scientists recorded some of the most intense solar flare activity in the sun's 11-year cycle Monday, and report that the activity can affect radio transmitters and, in rare cases, ground equipment.
That even a short outage would be quickly noticed speaks to the depth of the service's market penetration. AOL claims its 25 million instant messaging users send 656 million messages each day. AOL has approximately twice as many instant messaging subscribers as either of its nearest competitors -- Microsoft and Yahoo.
"This has a lot more business impact than businesses realise," said David Smith, vice president for Internet strategy at Gartner Group. "There are more people using it ... even though there are often policies against it." Companies often consider the instant message system a security breach, he said -- for example, messages aren't encrypted. Smith notes, however, that secure alternatives suitable for business communication have not been sufficiently developed.
"There are the beginnings of them ... Microsoft Exchange 2000 has instant messaging built into it, and a lot of people don't realise it," he said. "But I haven't heard of enough people using it to tell if it works as an instant messaging platform for business."