Canadian BlackBerry manufacturer Research In Motion (RIM) said in a statement that a "service issue" had affected customers in Europe, the Middle East and Africa.
A spokeswoman said it was not clear what type of problems customers were facing or the extent of the disruption in the UK.
Blackberry UK managing director Rob Orr later said the issue had been resolved and that all affected services were operating normally.
He wrote on his Twitter page: "Some users experienced issues with BlackBerry services today. Apologies for any inconvenience caused. All services now operating normally."
RIM also issued a statement, saying: "Our apologies to any customers impacted by the BlackBerry service issue today. We can confirm that services have been restored and are now operating normally."
The outage came after millions of BlackBerry customers endured three days of disruption due to a "core switch failure" last October.
RIM's shares fell to a nine-year low in June after Morgan Stanley (EUREX: DWDF.EX - news) downgraded the stock, saying the company's challenges were piling up. The firm also had to make 5,000 job cuts.
The launch of their latest phone operating system - BlackBerry 10 - has been delayed. It is seen by many analysts as the Canadian company's last roll of the dice in the battle with rivals such as Samsung and Apple (NasdaqGS: AAPL - news) .
The delay means they will miss the lucrative Christmas market.
The timing of the latest outage could not have been worse for BlackBerry, with huge queues outside Apple stores as the new iPhone 5 goes on sale.