Help w/ HTML

For those of you who don't already know, I do the monthly calendar and newsletter for the science-fiction club I'm a member of. It gets posted to the web - I generate the HTML using my current text editor, and upload it. There's a CSS file that was generated by the domain webmaster - I don't touch it.

The question is, why are these two pages different?

http://www.mnstf.org/einblatt/einblatt-200612.html
http://www.mnstf.org/einblatt/einblatt-200701.html

As near as I can tell, the former has body text bolded all the way through, and the latter doesn't. But I can't see anything that would cause that. Help?