Installed User Meta and after actvation the background of my site changed. Checked all my setting and even changed the background but it stayed the same. Unpon some investigation I found that User Meta was injecting a Template.css into my site. This plugin is all backend other than a shortcode so I do not see why it would even be attempting to put a css file into the mix.
I would suggest that if you use this plugin that you be very careful, not very nice behavior in my opinion.