RIM's system is relatively reliable, but its centralized structure means that any problems can affect millions of users.
In February 2008, an upgrade to the wireless system apparently caused a three-hour service disruption. In April 2008, a minor software upgrade crashed the system. A smaller disruption in September 2008 also was caused by a software glitch.
After initially focusing on corporate customers, RIM has expanded its reach into the consumer market in recent years. The devices face increasing competition from devices such as Apple's iPhone, Palm's Pre and the Motorola Droid.
RIM, which is based in Waterloo, Ontario, was scheduled to release quarterly earnings Thursday afternoon.
