Extra space inserted before first word in Excerpt

please post a link to your site, where the problem can be seen.

seems to be coming from this output by some ‘social ring button’ (?) plugin:

<div style="clear:both;">&nbsp;</div>

which ends up in the excerpts as a single ‘non-breaking-space’ character  

as a first step try to temporarily disable the plugin;
if this helps, try digging into the plugin code to replace   with an ordinary space character.