This plugin hasn't been through the quality control process as far as I can tell. Read some of the comments here:
http://www.viddler.com/forums/support/3631/
One of the issues is code inside is looking for a plugin in this location:
/wp-content/plugins/viddlercomments/
The readme.txt talks about this, but it is not included in the package as stated:
1. Unzip the attached viddlerwpcomments.zip file
Bottom line - if this plugin is going to work, it needs some attention.
http://wordpress.org/extend/plugins/the-viddler-wordpress-plugin/
