I just set up a fresh install of D7.22 and enabled AT Core and Pixture Reloaded and am getting this error:

Notice: Undefined index: leaderboard in include() (line 107 of /.../sites/all/themes/adaptivetheme/at_core/templates/page--full-width-wrappers.tpl.php).

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Notice: Undefined index: leaderboard in include() (line 107 of /.../sites/all/themes/adaptivetheme/at_core/templates/page--full-width-wrappers.tpl.php)

Same issue here.
Drupal core 7.23, adaptivetheme 7.x-3.x, AT Commerce 7.x-3.0-rc1+0-dev

Appeared when I enabled "Full Width Wrappers" in the markup overrides section of appearance settings
The issue disappears when I un-check the "Full Width Wrappers"

This option won't work with some themes, the fix here is for me to remove that option for themes that do not support it.

#1829496: Undefined index: leaderboard in include() (line 104 of ...adaptivetheme\at_core\templates\page--full-width-wrappers.tpl.php).

Marking as duplicate, apologies but this cannot be fixed right now, instead I have disabled this option in the latest dev of PR, please see the other issue for a longer explanation.