I have with several citations in a text the problem that the first name is included in the citation (John Meyer 2008) instead of (Meyer 2008). I cannot see a regularity as to which citations have the problem and which don't. The problem does not disappear when I change the style (I switched from American Sociological Association to Chicago and to American Political Ass.).
However, I found out that when I changed the authors first name in the database (say from John to James) , for the given entry (and all other entires of the same author!) the problem disappears.
(mac OSX 10.5.8, firefox 3.5, zotero 2.0 b6.5, though the problem appeared already in previous versions of zotero)
sorry, just saw the previous discussion here:
http://forums.zotero.org/discussion/3096/first-name-letter-in-citation/
(couldn't delete my post, how does this work?)