Research In Motion Ltd. has apologized for any inconvenience a recent outage has caused. BlackBerry email service in North America was restored for some users Wednesday morning following its second outage in less than a week.

Research In Motion Ltd. said Wednesday the root cause is still under review, but its preliminary analysis has determined there was a flaw in two recently released versions of its BlackBerry Messenger instant messaging software.

RIM has also provided a new version of BlackBerry Messenger (version 5.0.0.57) and is encouraging anyone who downloaded or upgraded BlackBerry Messenger since Dec. 14 to upgrade to this latest version, which resolves the issue.

RIM said late Tuesday that technicians were working to resolve email messaging delays on its BlackBerry smart phones in North and South America.

But by Wednesday morning, many BlackBerry users posting on the social networking site Twitter reported their service was back to normal.

RIM said message delivery was delayed or intermittent during the service interruption, but phone service and SMS service were unaffected. The Canadian company said it has taken corrective action to restore service.

During Tuesday's outage, users in the Americas were unable to send or receive email messages. Some said they also could not connect to the internet.

Waterloo, Ont.-based Research in Motion in a statement apologized for any inconvenience experienced by customers.

BlackBerry service last went out last Thursday. At the time, Research In Motion said technicians had isolated and resolved the issue and were investigating the cause of the outages. The company didn't say how many users were affected or how long that outage lasted.

The BlackBerry faces increasing competition from devices such as Apple's iPhone, Palm's Pre and the Motorola Droid. AT&T, in particular, has had had trouble keeping up with wireless data usage of the iPhone, which it carries exclusively in the U.S. Heavy data use by people watching videos and running powerful applications on their devices has led to dropped connections and long waits for users trying to run programs.

Previous outages

Three-month stock chart for RIM on the TSX (CBC)

In June 2008, customers of Bell Canada's BlackBerry wireless service experienced disruptions in the hand-held device's email, video streaming and web browsing functions.

This outage followed a failure a week earlier, when all BlackBerry functionality was taken offline for four hours as the device's maker, Waterloo, Ont.-based Research In Motion Ltd., completed a planned upgrade to the servers that run the technology.

RIM also had to deal with a major unscheduled outage in February 2008, which took down 12 million customers for about three hours during the middle of the day.

Though major service disruptions have been rare, the failures have spurred an angry backlash against the company because of its typically lengthy silences about the reasons for problems. When BlackBerry service suffered a major outage in April 2007, the company remained silent about the cause for two days.

Duncan Stewart, an analyst at DSAM consulting, said the second outage in less than a week raises some troubling questions for the company.

"RIM has a totally unique architecture for handling messages," he said. "Is their solution inherently vulnerable?"

He also suggested that the company's strong push into the consumer market in addition to its business base might be destabilizing the network somewhat. A big advantage RIM has had over Apple Inc.'s iPhone has been its reliability, he noted.

"If it becomes less reliable, thus endeth the advantage," he said.

With files from CBC News