This tutorial works not only for the smart sharing plugin and thesis 1.7 theme but for any other plugin and theme too if they are giving same error.
I was using another plugin before, named digg digg but it was quite heavy in my opinion so i replaced it with this light weight plugin named smart sharing plugin. But after activating and configuring the plugin it never showed on the blog
To be able to fix the slider not showing in some wordpress themes (thesis 1.7 in my case) follow these steps:
1. Goto plugins > editor
2. Select your plugin (i.e smart sharing plugin)
3. Goto line 62 and replace this code:
add_action( 'get_footer', 'add_smartsharing' );
with this (changed get_footer to wp_footer) :
add_action( 'wp_footer', 'add_smartsharing' );
4. Save the file and confirm that the plugin is working fine now.
It can be tried to work inversely, like if your plugin and theme are not compatible, and have wp_footer in it already, try changing it to get_footer to see if it works.
If you still have any difficulty do let me know.