Applies to Magento 1.4 installations
For Magento 1.5 version and above please check this article
The following error (or similar) is shown in Magento Connect Manager on installation/upgrade:
ERROR: unable to unpack downloader/pearlib/download/AW_Blog-1.0.21.tgz
There is a bug in current stable PEAR/Archive_Tar implementation resulting in impossibility to unpack archives made by certain software versions.
The patch has been already applied for our new installations. If you notice this issue with your old Magento installation, please notify our Support Team to get this fixed.