There was a big outage in April, then one in September then one in October, and now angry BlackBerry owners are reporting that their service went down again on Monday.

Research on Motion (RIM) which owns BlackBerry has admitted that it suffered a "critical severity outage" affecting users in the Americas.

RIM's worldwide subscriber base had reached about 12 million people by late last year, but it was only subscribers across the Atlantic that were affected.

The outage came on the eve of three US presidential primaries, hitting politicos and those in the business community alike.

RIM notified its clients of the outage in an email (ironic!).

"This is an emergency notification regarding the current BlackBerry Infrastructure outage", RIM support account manager Bryan Simpson said in an email sent to large clients.

RIM said in a later statement that data services in the Americas experienced delays on late Monday afternoon, around 3.30pm Eastern time, but services were restored in the early evening at around 6.30pm.

However, Reuters reports that by about 7:00pm Eastern time, only some users said emails were trickling through while others continued to be without service.

US ISP Verizon Wireless said the outage was affecting all carriers' BlackBerry email service in North America, but that its customers could still make calls on their BlackBerry throughout the outage.

Meanwhile in Canada, BlackBerry owners were also hit and the country's three main carriers - Telus, Rogers Communications and BCE - all pointed thr finger at RIM.

"It is a RIM issue", Odette Coleman, a spokeswoman for Rogers Wireless in Toronto, told the Financial Post. "It is everybody who carries a BlackBerry with any carrier."

In Canada, most problems started around 3:20pm Eastern time, and service for many users had normalized about four hours later.

While there have been minor outages in the past few months, the last major outage was in April 2007.

At the time, co-chief executive Jim Balsillie said such incidents were "very rare" and RIM was taking steps to prevent it from happening again.