Online game players using Microsoft's Zone site complained of persistent problems accessing the service on Tuesday, as Microsoft required all users to switch to its Passport authentication service. In a notice posted on the Zone home page, Microsoft informed users that they must sign up for the Passport online identification service, a controversial element of the company's .Net online services push. "The Zone is now a Microsoft .Net Passport site!" the notice read. "Your existing Zone account still works, but you must first sign in to .Net Passport or register for a new .Net Passport account." The Zone is a part of Microsoft's MSN online empire. It includes hundreds of games, ranging from roleplaying fantasies to card games, where users compete with each other online. Some games, such as the popular roleplaying game "Asheron's Call," require monthly subscription fees. Under the Passport switch, all Zone users have to link their Zone account to an existing or newly created Passport account. Darren Gasser, a software developer and regular "Asheron's Call" player, said he had no problem creating a Passport account on Tuesday. But he couldn't get through to the Web site that was supposed to link the new Passport account to his existing Zone account, an experience echoed by numerous Zone users reporting their experiences in online forums. "All I got was a whole load of 'server overload' and other kinds of error messages," Gasser said in a phone interview. "That's what I'm hearing from everyone I know -- they can't get through to link Passport to their Zone account." Gasser said many "Asheron's Call" users were locked out for three days or more the last time Microsoft did a major overhaul of the Zone, about a year ago. The company had promised in various messages and online forums that this transition would go more smoothly. "They kept assuring (us) this was all done using proven .Net technology," he said. Microsoft representatives were not available late on Tuesday to comment on the extent or nature of Zone access problems. One problem identified by several posters to online game forums was that the old Zone login system allowed 16-character passwords, while Passport limits passwords to 15 characters, shutting out security-conscious gamers trying to log in with their existing account information. Microsoft is pushing Passport as a one-stop service for identifying users at online outlets ranging from calendar services to shopping sites. Privacy groups and others have complained the service lacks adequate safety measures for securing sensitive user information, charges that Microsoft denies. For everything Internet-related, from the latest legal and policy-related news, to domain name updates, see ZDNet UK's Internet News Section. Have your say instantly, and see what others have said. Click on the TalkBack button and go to the Telecoms forum. Let the editors know what you think in the Mailroom. And read other letters.