Drush 4.5 breaks Aegir completely

I'm not sure if this is our "bug", or rather compatibility issue introduced by Drush folks in recent release, but the result is that it is not possible to install or upgrade Aegir or do anything with sites (like migration etc.)

On Aegir install the errors are as below:

copy(/data/disk/o4/config/includes/nginx_advanced_include.conf): failed to open stream: No such file or directory                     [warning]
provision.file.inc:38 [1.81 sec, 9.79 MB]
copy(/data/disk/o4/config/includes/nginx_simple_include.conf): failed to open stream: No such file or directory                       [warning]
provision.file.inc:38 [1.81 sec, 9.79 MB]
copy(/data/disk/o4/config/includes/fastcgi_params.conf): failed to open stream: No such file or directory provision.file.inc:38       [warning]
[1.81 sec, 9.79 MB]
copy(/data/disk/o4/config/includes/fastcgi_ssl_params.conf): failed to open stream: No such file or directory provision.file.inc:38   [warning]
[1.81 sec, 9.8 MB]
copy(/data/disk/o4/config/includes/upload_progress_test.conf): failed to open stream: No such file or directory                       [warning]
provision.file.inc:38 [1.81 sec, 9.8 MB]

Bootstrap to phase 5. [48.67 sec, 10.8 MB]                                                                                          [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_root() [48.67 sec, 10.8 MB]                                                         [bootstrap]
Loading drushrc "/data/disk/o4/aegir/distro/001/drushrc.php" into "drupal" scope. [48.67 sec, 10.8 MB]                              [bootstrap]
Initialized Drupal 6.22 root directory at /data/disk/o4/aegir/distro/001 [48.67 sec, 10.8 MB]                                          [notice]
The drush command '@self provision-install-backend' could not be found. [48.67 sec, 10.81 MB]                                           [error]
Could not find a Drupal settings.php file at ./sites/default/settings.php. [48.67 sec, 10.81 MB]                                        [error]
Undefined index:  login_link install.provision.inc:60 [48.67 sec, 10.81 MB]                                                            [notice]
Drush was not able to start (bootstrap) the Drupal database.                                                                            [error]
Hint: This error often occurs when Drush is trying to bootstrap a site that has not been installed or does not have a configured
database.

Drush was attempting to connect to : 
  Drupal version    : 6.22
  Site URI          : o4.linode.us.host8.biz
  Default theme     : garland
  Administration theme: garland
  PHP configuration : /usr/local/lib/php.ini
  Drush version     : 4.5
  Drush configuration: /data/disk/o4/aegir/distro/001/sites/o4.linode.us.host8.biz/drushrc.php
/data/disk/o4/aegir/distro/001/drushrc.php
  Drush alias files : /data/disk/o4/.drush/hostmaster.alias.drushrc.php /data/disk/o4/.drush/server_master.alias.drushrc.php
/data/disk/o4/.drush/platform_hostmaster.alias.drushrc.php
  Drupal root       : /data/disk/o4/aegir/distro/001
  Site path         : sites/o4.linode.us.host8.biz
  Modules path      : sites/o4.linode.us.host8.biz/modules
  Themes path       : sites/o4.linode.us.host8.biz/themes
  %paths            : Array

You can select another site with a working database setup by specifying the URI to use with the --uri parameter on the command line
or $options['uri'] in your drushrc.php file.
 [48.67 sec, 10.81 MB]

On Aegir upgrade the errors are:

Deploying site from /data/disk/o1/backups/o1.linode.us.host8.biz-20110815.151949.tar.gz [56.09 sec, 15.14 MB]                         [message]
Failed to extract the contents of /data/disk/o1/backups/o1.linode.us.host8.biz-20110815.151949.tar.gz to  (The target directory         [error]
could not be written to) [56.09 sec, 15.14 MB]
Changes made in drush_provision_drupal_pre_provision_deploy have been rolled back. [56.09 sec, 15.14 MB]                             [rollback]
Changes made in drush_db_pre_provision_deploy have been rolled back. [56.09 sec, 15.14 MB]                                           [rollback]

On site migration the errors are:

Deploying site from /data/disk/o1/backups/crm4.o1.linode.us.host8.biz-20110815.163408.tar.gz
Failed to extract the contents of /data/disk/o1/backups/crm4.o1.linode.us.host8.biz-20110815.163408.tar.gz to (The target directory could not be written to)
Changes made in drush_provision_drupal_pre_provision_deploy have been rolled back.
Changes made in drush_db_pre_provision_deploy have been rolled back.