I tried to bring back the sidebar, install it in different blogs, install it in a new blog, install old versions of the plugin, and oddly enough, none of them seems to work.
Everytime, I get the same message, saying it caused a fatal error because of line 60 (on the earliest version of the plugin, it's line 29)
The line goes as follows:
$curYear = ($sna_options['desc_order']) ? $year_results[0]->post_year : end($year_results)->post_year;
Unlikely hypothesis on why it doesn't work may be because I'm testing it in a local server, maybe when I transfer the blog to its real location, it works. And I'm using Wordpress in Portuguese as well, maybe it affects the date format somehow.