That looks familiar ... I think it looks a lot like the times I was trying to play with php ini file and change the include_path ... when I had the include_path wrong, the database was not connected to either in the config file or another critical file after that ...
I'd be willing to bet if you went to yoursite.com/admin/ you might see an admin login ... and if you do and if you did ... if you turned on show errors/de-bugging in preferences, you'd see a database error msg from php .
That's one guess. It really looks familiar like the database is not connected or only on one call .
The other guess is the script file installed for gorgle ads has a syntax errorand it wipes the entire remainder of the content, and that's why you have header and footer but blank content.
syntax error in the theme file that wipes entire content of page ...
let us know if you find out what is was?