BlackBerry users are today facing a third day of problems with their services as BlackBerry maker RIM struggles to fix a "core switch failure", with a failover system that it said "did not work as previously tested".

The problems are already raising serious compensation questions, as well as concerns over the viability of RIM's backup plans.

BlackBerry users across Europe, Africa, the Middle-East and parts of South America have had intermittent emails, instant messaging and web access, with messages arriving hours late in large batches. The BlackBerry service came back briefly this morning at around 5am UK time after a 17-hour outage which started at around 12pm the previous day (Tuesday).

Emails from the previous day were downloaded onto users' BlackBerry devices, but then the service cut out again before briefly returning at about 9am. The service for emails and other services then crashed for users at about 9.30am.

In the latest RIM statement, sent out to the press at 10pm last night, it said the problem was down to a "core switch failure within RIM's infrastructure". It added: "Although the system is designed to failover to a back-up switch, the failover did not function as previously tested."

Questions will now be asked as to how often RIM makes these tests and whether the back-up facilities are indeed at a different data centre from the one in Slough, which is believed to be at centre of the problem - something which RIM won't comment on.

If a company relies on providing a service to millions of customers from a single data centre, with no separate back-up site with its own individually tested architecture, it could face difficult questions.

Twitter users are continuing to use their PCs to voice their frustration at the continuing problems that have plagued RIM since Monday morning.

Rebecca Lammin tweeted: "Retweet if you don't have a life because your #blackberry isn't working." Peter Jones added: "#Blackberry's having a PR nightmare, as well as a technological one. How about communicating with customers? Explaining? Apologising? Assuring?"

According to Gulf News mobile operators Etisalat and du will refund both their contract and pre-paid users for the lost three days of service due to the outage.

So far most UK mobile operators have not addressed the issue of compensation for their users, paying for a service they are not getting. T-Mobile UK told's sister site in the US that any question of compensation due would "be a matter for RIM to resolve".

As the mobile operators are paying RIM to provide a service to their customers, who directly pay their mobile operator for that service, users are likely to expect those operators to demand compensation from RIM with the view to getting a refund passed onto them.