The creators of APE (Application Enhancer) have denied that their application-enhancement framework is responsible for the blue-screens when Macs are upgraded to the newly released Leopard.

Apple, however, has blamed the software in a support document advising users to delete APE from their machines.

Within hours of Leopard’s debut on Friday, users began reporting a “blue screen of death” that appeared after running the default Upgrade option. On affected Macs, the blue screen stymied the required restart after the install, locking users out of their computers.

The Installation and Setup forum on Apple’s support site was quickly flooded with messages, including one that fingered Unsanity’s APE, software required to run Mac customising haxies such as ShapeShifter, as the culprit. A user identified as Chris Mcculloh posted instructions on manually deleting APE using the Unix command line to kick the Mac through the restart.

Others spread Mcculloh’s instructions to new threads on the Apple forum, and reports of success poured in. “This fix seemed to work perfectly for me,” said TuHolmes.

But Unsanity in an email to sister publication ComputerWorld, denied its APE was involved.

“APE has an artificial block implemented so it refuses to load,” said Rosyna Keller of Unsanity. “It checks the version number and, if it is 10.5, bails. No other code is executed from APE and at no time are any APE modules loaded.” Keller said he had installed Leopard on three different APE-equipped Macs without problems.

“The only possible way APE could even remotely, theoretically be involved is if they are using an over two-year-old version of APE (1.5.1 or 1.5, May, 2005). But if they’re on an ICBM [Intel Chip Based Mac], this is not a possibility as we never released an APE that was compatible with the ICBMs that did not have the system version check.”

Unsanity added a caution to a standing compatibility note on the home page of its website at the weekend: “Please make sure you have Application Enhancer 2.0.3 or later installed before you upgrade to Mac OS X 10.5.” It also sent email to members of its mailing list that contained the same advice.

Apple, however, appeared to have decided that APE was the cause of some, if not all, of the blue screens. In a document added to its support database late Friday, the company said “third-party ‘enhancement’ software” may be the cause, then listed as one of two possible solutions deleting the same four APE files as Mcculloh had highlighted earlier.

Keller said Apple got it wrong, too. “In this case, it’s the deletion of Library/Preferences/com.unsanity.ape.plist [one of the four files marked by Mcculloh and Apple for deletion] that shows that no one has actually bothered to troubleshoot this issue,” he said. “This file does nothing. It only exists to tell APE to disable itself if you open the APE prefpane and click ‘Temporarily Disable.’

“You’ll always have people suggesting voodoo solutions to problems (like repairing permissions) and them claiming it works when simply rebooting was the fix,” Keller added.

Some users reporting blue screens - who had reinstalled Leopard, the second time successfully, by using the Archive and Install option - swore they did not have APE on their Macs or that the fix did nothing to fix the problem. “I’ve tried both fixes posted in this thread - Archive [and] Install and Application Enhancer removal - to no avail,” said rweissman01 on the Apple support forum.