My b2evolution Version: Not Entered

I just upgraded from 1.9.1 to 2.4.2 on a friends website. Initially I got all kinds of error messages and thought the database was toast. But after blowing out my cookies, I can get to the login screen. After the login, however, I get the following:

Fatal error: Call to a member function on a non-object in /home/pathtoblog/blog/inc/_main.inc.php on line 447

If I try and go to the blog page I get this message:

Fatal error: Call to a member function on a non-object in /home/pathtoblog/blog/index.php on line 59

I've been using B2Evo for about 3 years now and have done tons of upgrades without a hitch. The upgrade went fine - no errors shown. I'm kind of at a loss at this point. Any suggestions would be greatly appreciated.