www.reuters.com:By Georgina Prodhan LONDON (Reuters) - Millions of BlackBerry users around the world were left without text communication services for a third day on Wednesday as Research in Motion struggled to fix what it said was a switching failure in its private network. Users in Europe, the Middle East, Africa and India suffered patchy email service and no access to browsing and messaging, ratcheting up negative sentiment toward a company already losing market share to Apple and Samsung. RIM, which had said on Tuesday that services had returned to normal, said later the problems had actually spread beyond EMEA and India to Argentina, Brazil and Chile. "The messaging and browsing delays ... were caused by a core switch failure within RIM's infrastructure," it said. "As a result, a large backlog of data was generated and we are now working to clear that backlog and restore normal service." The service disruptions are the worst since an outage swept north America two years ago, and come as Apple prepares to put on sale its already sold-out iPhone 4S on Friday. "It's a blow upon a bruise. It comes at a bad time," said Richard Windsor, global technology specialist at Nomura. "One possibility could be that it encourages client companies to look more at other options such as allowing users to connect their own devices to the corporate server and save themselves the cost of buying everyone a BlackBerry." Many companies, no longer seeing the need to pay to be locked into RIM's secure proprietary email service, have already begun allowing employees to use alternative smartphones, particularly Apple's iPhone, for corporate mail. RIM has made inroads into the youth market attracted by its free BlackBerry Messenger (BBM) service, partially compensating for its losses in the corporate market. But new products like its PlayBook tablet computer have been poorly received. Following a dismal set of quarterly results and a plunge in its share price, some investors are now calling for a break-up, sale or change of management at the company. Increasingly frustrated users tweeted their frustration on Wednesday, while RIM's own official Twitter feed was last updated on Tuesday night, saying problems were being resolved and it was sorry for the inconvenience. Veteran British entrepreneur Alan Sugar, who founded electronics company Amstrad in 1968, tweeted: "In all my years in IT biz, I have never seen such an outage as experienced by Blackberry. I can't understand why it's taking so long to fix." Some customers used humor to deal with the situation. One joke making the rounds on Twitter said: "What did the one BBM user say to the other? Nothing." (Editing by Greg Mahlich) Copyright 2011 Thomson Reuters. Click for Restrictions.