Mac users installing Apple's recent security update that patched 67 bugs, have reported an unusually high number of problems.

According to messages posted on Apple's support forum, some users have had trouble downloading the update, while others have seen their Macs hang with a blue screen during installation.

"I've made three [download] attempts, and every one of them has failed with an error message telling me that the digital signature for the package is incorrect, suggesting that it may have been tampered with since being signed," a user identified as 'jposner said. Other users confirmed seeing the same message.

Users who were able to download the 442MB update watched as their Macs stalled during its installation. "I just installed 10.5.7 on two machines... in both cases, after the installation the computer went into some sort of a loop with a blank blue screen," said 'Lazarus Long' in another support forum thread.

"I finally had to shut down hard and then wait for two or three reboots until I could login." Dozens of other users reported the same problem on the thread.

Still others reported missing external disk drives and disappearing display resolutions. "After updating to 10.5.7 on my Mac mini, my monitor is not recognised correctly any more!" said 'cizko'.

"It should be running at 1920x1200 native resolution but is now stuck on a bizarre 1920x1080."

The MacFixIt site, which closely tracks problems with Apple's updates, posted recommended steps for several of the snafus. For example, it urged users to download the Combo Update - a much larger 729MB file - rather than using Software Update to avoid the incorrect digital signature problem.

MacFixIt also culled recommendations from the Apple support forum for the blue screen and display resolution issues, advising that users boot into Safe Mode or step through a five-step process for the former, and that users try a PRAM reset for the latter.

Some users were furious over the difficulties the update posed. "That had to be the worst OS update from Apple I've installed over the last 5 years," said 'Seanrobrien on a support thread.