A Monday update to Apple's Leopard operating system is causing a host of problems for users, ranging from broken Bluetooth connections and no sound to large popping noises during boot-up and dead USB ports.

A Monday update to Apple's Leopard operating system is causing a host of problems for users, ranging from broken Bluetooth connections and no sound to large popping noises during boot-up and dead USB ports.

The OS X 10.5.6 update is supposed to improve a number of features, including synching between the address book and the iPhone, roaming capabilities of AirPort connections on Intel-based Macs, an encryption alert that appeared in the chat window of iChat, and improvements to gaming performance.

It is also supposed to prevent Mail from quitting, fix an issue that allows junk mail to remain in the inbox, and improve MobileMe synching time. The update also addresses an issue that prevents parentally-controlled accounts from accessing the iTunes Store, and improves compatibility with Web proxy servers in Safari.

Many users, however, are reporting on the Apple forums that after the initial installation, their Macs remain frozen on "configuring setup." Others who have made it through the installation process found that their devices no longer recognize the mouse, sync with Bluetooth, open Suitcase Version 2, or connect to the AirPort wireless network, among other issues.

"Post 10.5.6 I get a loud pop during the very end of the grey startup screen or right after the time verbose mode goes to a blue screen," one user wrote on the Apple forums.

"The latest version of Leopard (10.5.6) downloaded automatically via Software Update," wrote another user known as Davald. "However, when I attempted to install, the process hangs on 'configuring setup.'"

After 15 minutes, Davald did a forced restart, which returned his MacBook Pro to 10.5.5.

Another user found that after he typed his password, the screen went blue, and then returned him to the login screen.

Some people found workarounds, like installing the regular update instead of the combo update from the Apple download page or removing update files, but there does not seem to be one solution that works for all users. Some users are having no issues with the update at all.

Some lashed out at Apple. "This is why I decided to cross-over to 'The Darkside' and purchase a Dell," wrote someone who identified himself as Gabriel Cobos1. "Once upon a time, nothing was better than an Apple. Then I bought a new [MacBook Pro]... actually two of them, and all of them died, trying to do what I do with simple ease with my homebuilt PC's."