The companies confirmed that some people had experienced technical difficulties, such as the inability to receive or send e-mail. They said the exact number of affected accounts could not be determined.
An MSN representative said the difficulties affected a small number of customers who had entered account information incorrectly when they were switched over from a previous Internet service provider run by Dell through partner UUNet.
"We do know it's been limited," said Bob Visse, group product manager for MSN. "It's been mostly cases where?there were some specific instructions that needed to be followed in order to set up their accounts correctly."
About 10 percent to 20 percent of Dell's 1 million previous ISP subscribers switched to the new DellNet service, according to Dell. Announced last June, the deal included a free one-year subscription along with a Dell Dimension or Inspiron computer.
The service complaints come as Microsoft faces other headaches with its ISP marketing plans, having just rescinded a $400 rebate on its MSN service last month, citing costs.
MSN's Visse said the problems experienced by DellNet customers have been solved and the issue is over.
Dell also downplayed the complaints, saying that it is continually working with MSN to improve service.
"Obviously, we're still the point of accountability for these customers even though MSN is running the service," said Dell spokesman Bryant Hilton. "But with any product there's probably going to be a couple of consumer complaints, and we do what we can to get those resolved."