nternet phone service Skype was today racing to fix a technical glitch that is thought to have left millions of users unable to log in. The embarrassing setback comes just two weeks after Microsoft bought the firm for £5.2billion, prompting claims the outage was caused by efforts to integrate systems. It first affected users yesterday afternoon and this morning subscribers were still complaining that they couldn’t sign in. Yesterday Skype claimed the problems affected only a ‘small number’ of its more than 660million users. But the fact that its website was also briefly taken offline suggests that the number of subscribers failing to sign has in run into millions. Messages about the disruption have appeared from several countries on Twitter. This morning an American user, ocrapitsj, tweeted: ‘What's Happening? SKYPE IS NOT WORKING!’ Jamie Barton, from North East England, added: ‘It just quits on open. What a load of junk.' And New Yorker MidnightHerald posted the comment: ‘Had an interview scheduled via Skype this morning. What do I wake up to? A veritable skypocalypse.’ Problems were first reported yesterday afternoon. On its own Twitter account, at 1.30pm, Skype officials wrote: ‘Some of you may have problems signing in to Skype and making calls.’ Eventually, almost 12 hours later, Skype posted a solution for Windows users by going to the website: http://bit.ly/jwUhAx. The firm, based in Luxemborg, also issued a temporary manual fix for the problem that involved deleting a file call ‘shared.xml’ from the its programme folder. It follows another major breakdown in December that affected 15million users and left callers were cut off in mid-conversation. At that time Skype promised an overhaul of its servers to avoid further outages. Whatever the cause of this latest failure, it will embarrass Microsoft, which bought Skype on May 10 in its largest ever acquisition. Analysts questioned whether its technology and relatively small revenues justified the multibillion-pound price tag. But Skype founder Niklas Zennstrom said the software giant could help expand the phone service and improve video call quality. ‘Skype's full potential hasn't been realized yet,’ said Zennstrom in an interview at the e-G8 forum in Paris yesterday, saying improvements in networks and devices such as smartphones meant the experience of using the service was still getting better. ‘I think that Microsoft has a huge opportunity to integrate it into a lot of their different services,’ said the Swedish entrepreneur and venture capitalist. Zennstrom, who along with partner Janus Friis started Skype in 2003 and grew it into an online giant with 145 million users a month, no longer has a management role at Skype and will sell all his shares once the deal with Microsoft closes. Asked how Microsoft could incorporate Skype into its business, Zennstrom declined to provide specifics, adding that it was up to the software giant to comment. ‘Of course they have so many different assets. If they do a good job integrating Skype, the company can grow even more.’ Microsoft could combine Skype with its software such as Outlook to appeal to corporate users, while the voice and video communications could link to Microsoft's Xbox live gaming. Skype also would offer Microsoft another route to develop its mobile presence, an area into which it has already put more energy and resources - for example through a partnership with Nokia - as PC usage comes under threat. A Skype spokesman said the firm did not know how many users were affected by the worldwide problems but again insisted the number was ‘small’.