Apple Inc rolled out its new iCloud service and latest mobile software to a chorus of user complaints this week, after glitches led to email access problems and long delays in installation.

Some users reported losing their email access as Apple formally launched iCloud, an online communications, media storage and backup service, on Wednesday.

Apple's new operating system for the iPhone, iPad and iPod Touch -- iOS 5 -- also annoyed many users who encountered hours-long delays in downloading and installation.

Investors have high hopes for iCloud, which replaces MobileMe, a collection of Web-based products that have failed to impress critics or generate substantial revenues for a company that has had success in most other ventures over the past decade.

It failed in a very nasty way in that mail sometimes vanished, sometimes appeared then vanished, and often there was a user and/or password-incorrect message plus some rather obscure additional error messages, said David Farber, a professor of engineering and public policy with Carnegie Mellon University.

The behavior suggests program problems, added Farber, a well-known computer scientist.

But the iCloud problems are especially embarrassing for Apple, as the company introduced the new online service with much fanfare in June at its annual developer forum.

Co-founder Steve Jobs, who died last Wednesday, said it just works when he introduced the service in June. The software is key to the new iPhone 4S, which will be launched on Friday in seven countries.

The problems also come as rival Research in Motion deals with an international outage of its email and messaging services.

Some users were experiencing intermittent authentication errors when trying to use mail, Apple said in a status update on its webpage for iCloud support. Normal service has been restored. We apologize for any inconvenience.

Other problems Apple reported as having resolved included: intermittent slowness when signing in to iCloud, users unable to back up their data, and delays receiving verification emails from Apple.

Apple spokespersons did not immediately return calls seeking comment.

Users took to Twitter to complain about the problems during the roll-out.

iCloud would be great if the email would freaking recognize my password, wrote Leanna Lofte, or @llofte, on Twitter.

Apple Mail's still offline, everything's out of sync here between my devices, and what a mess, Matt Peckham, or @mattpeckham, wrote on Twitter.

(Reporting by Poornima Gupta in San Francisco and Jim Finkle in Boston; Editing by Richard Chang)

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