I'm working through i18n on my plugin and tried to use the add-textdomain.php module. Looks like a commit to makepot.php on Dec 20, 2010 removed the $keywords variable from the MakePOT class which breaks add-textdomain.php.
I'm using makepot.php from: http://svn.glotpress.org/trunk/pomo
The online version appears to also be broken.
As a temporary workaround I put the $keywords definition back into makepot.php and was able to process my files.