Apple’s latest mobile OS update and cloud storage technology have prompted user complaints following their launch, according to various reports.

Users who have attempted to install the new iOS5 operating system – for iPhone, iPad and iPod Touch devices – have experienced lengthy delays in the installation process of the OS, with many attempted upgrades failing.

Numerous users received the Error 3200 message during installation of iOS5, caused by Apple’s servers failing to fulfil authorisation requests from devices. AppleInsider reported that this was due to the sheer number of users trying to update their devices with the OS.

The problem meant that some users were left with unusable devices, as the handsets were unable to access Apple’s authentication service to reactivate the phone. The Apple Support Communities forum also received reports of 3004 error messages, in which iTunes is unable to connect with Apple’s update server, causing devices to become bricked.

AppleInsider added that successful requests to upgrade to iOS5 have meant a 15 minute download process, with the backup process now taking up to three hours.

Meanwhile users of the iCloud online communications, media storage and backup service, also launched this week, have reported losing access to email, slow sign-in and various error messages.

Posts on Apple’s iCloud Support website said some users may have been “unable to backup their data” and “were experiencing intermittent authentication errors when trying to use mail”. Apple said normal service had been restored and apologised for the inconvenience to users.

Apple has had some good news however, as Bloomberg reported that Yankee Group analyst Carl Howe has predicted it could sell as many as 4 million iPhone 4S devices this weekend. The iPhone 4S goes on sale today in Australia, Canada, France, Germany, Japan, the UK and US.

Bloomberg also reports that the newest version of the iPhone has sold out for pre-order at US operators AT&T, Verizon Wireless and Sprint Nextel. Apple said earlier this week that more than one million customers had pre-ordered an iPhone 4S during the first day in which it was available.

The iPhone 4S was unveiled last week to a relatively muted response following speculation that Apple would launch an all-new iPhone 5. The iPhone 4S features iOS5 as well as a faster processor, better quality camera, improved battery and the new Siri voice recognition functionality.