America Online Instant Messenger users experienced outages, dropped conversations or other missed messages for a number of hours April 4.
The AIM outage may be a symptom of a bigger problem, according to The SANS Institute.
Problems were also reported April 4 by customers of broadband provider Qwest Communications, and Network Solutions, which plays a central role in the day-to-day flow of the Internet.
A spokesperson for AOL, the Time Warner division that supports AIM, said the company is aware of the problems, but couldnt offer any additional information.
"We know that its an ongoing problem," the spokesperson said, and added that the company is looking for the source of the troubles.
The April 4 problems, and the resulting lost productivity, serves as a reminder of how AIM and other instant messaging features are being used by enterprises as a way for employees to collaborate.
The impact of the problem is hard to immediately assess, but it appears to be affecting a number of different U.S. regions.
AIM users located at work places in California, New York and the Boston metropolitan area say theyve been experiencing recurring two-to-three-minute outages, or finding their outgoing messages never make it.
According to a source not associated with Time Warner, AIM appears to be blocking messages using whats known as an OTR proxy, which secures instant messaging conversations so they cant be read by anyone, even the company providing the service.
OTR proxies are not a formal part of AIM, but can be added nonetheless.
The proxy is built into instant messaging features in Trillian, GAIM and others that allow for use of several different IM features at once.
Editors Note: This story was updated to include information from The SANS Institute and customers of broadband provider Qwest Communications, and Network Solutions.