I’ve noticed that when Comments Evolved for WordPress (http://wordpress.org/plugins/gplus-comments/) is installed with The Events Calendar Plugin from Modern Tribe,it breaks the admin css for event setting, and event settings on single events pages. It also causes problems with other form related items in the wordpress admin area.
I’ve been able to recreate the issue in a live and development settings with only these two plugins and also other plugins, both with premium and basic (2012) themes running.
Same situations. Activation of Comments evolved breaks Events Calendar and other admin forms css.
It turns form elements and meta boxes wild. Drop down are fully dropped down and always visible. Border around all form elements.
Just an FYI for those who might be running the two simultaneously and wondering why it’s doing it.
I’ve alerted the developers of the plugin. We’ll see what they say.
As an alternative, I’d recommend using Social Comments Plugin:http://wordpress.org/plugins/social-comments/
I have no affiliation with either company or plugin. just what I’ve noticed and used and liked.
Hope this helps.