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Symptoms

Virtual machine cannot start due to memory allocation problem. This issue appears after the 10.5.2 Apple security update. Unable to fix it by downgrading to the previous Parallels build.

Cause

The problem with memory allocation has been caused by the last major Apple security update. Right now the only way to overcome the issue is to downgrade Mac OS X 10.5.2 to 10.5.

Resolution

Please follow these steps in order to downgrade Mac OS X:

Solution A:

With 10.5.1 or later to 10.5:

1. Verify you made a Time Machine backup before you upgraded to 10.5.1 or later.


2. Boot off the Leopard installer disk.


3. Select the installation language.


4. Go to the "Utilities" menu and use the "Restore from Time Machine" backup to restore to your Time Machine state before you installed 10.5.1 (10.5.2).

This will only work, if you have no data to salvage from 10.5.1 or later.

Solution B:

1. Backup all your existing data to the external hard drive.


2. Write down registration codes for installing applications.


3. Erase and install the operating system with none of the backups connected to the machine during the erase and install process, and no peripherals other than display, keyboard and mouse attached.


4. Restore user documents that are capable of being downgraded.


5. Install from the original installation disks which shipped with your machine. For more info see http://docs.info.apple.com/article.html?artnum=61802.


6. Install from the third party CDs and downloads any other applications.

For more information visit Apple Discussions: http://discussions.apple.com/thread.jspa?threadID=1308817&tstart=0

From http://discussions.apple.com/thread.jspa?threadID=1308817&tstart=0

Topic : How do I downgrade my Mac OS X operating system