The workarounds posted on the AddThis forum are not EASILY added to the AddThis plugins..
Unfortunately for WordPress users the only way to use the AddThis code to your site is to add it in manually (which is what I plan to do.. I will be using the tip I posted here: http://support.addthis.com/customer/portal/questions/798770-html-validation-failed-using-encoding-as-an-alternate-solution-
Thankfully I am using a theme framework so I can control where this code appears and what pages it appears on.. Which is probably a better solution than using a plugin anyway..
I WISH the AddThis team would FINALLY make their code validate!!!!