Microsoft said on Tuesday that it had resolved problems that caused a significant outage affecting its MSN Messenger service worldwide.

A company representative declined to elaborate on the nature of the problem, or the steps Microsoft took in fixing it. In an earlier statement, the representative said the outage was caused by an "isolated issue that we've located in the data centre."

The problem had affected a "significant" number of MSN Messenger users intermittently since Monday afternoon, the representative said.

The latest outage comes days after security monitors discovered the Bropia worm was using MSN Messenger to spread. The Microsoft spokeswoman denied the outage was caused by the worm.

Last October, a glitch crippled many MSN Messenger users around the world. In March of last year, MSN suffered a couple of outages over a weeklong period. Some speculated that one of the blackouts was caused by sign-in problems from its Passport service. Microsoft denied Passport experienced any problems during the down period.

Instant messaging has become one of the most popular services among Internet users, and it's gaining more traction among businesses. Popularised by the AOL Instant Messenger, millions of Internet users now have an IM client loaded on their PC desktop.

While AOL, Microsoft and Yahoo account for most of these users, the three networks remain proprietary. Many consumers have more than one IM client running on their screen to chat with various contacts on different services. All three companies have stated their intention one day to interoperate, but results have yet to be seen.