I got an error installing ver 2.2 on joomla 1.5.7 with legacy turned on. The error related to an "index.html" not found. The solution was to reset the permission to that file to 755 instead of 644.

Otherwise, this is a really good addition and I have had it as part of every joomla installation. Keep up the good work! Hoping to see a 1.5 native version of this soon.