After a wiki migration under Mavericks, I had some wiki pages that were blank.
The history appeared to be intact but, setting the page to any version resulted in displaying the same blank screen.
To fix this problem:
Click the pencil to edit the page
Copy all of the text from the page with command + a, then command + c
Open an editor such as Text Wrangler, or Komodo Edit
Paste the wiki text using command + v
Copy all of the text back out fromthe editor with command + a, then command + c
Create a new wiki page
Past all of the text into the new wiki page using command + v
Click the save button
Note: When you paste into Text Wrangler, Komodo Edit (or any editor that does not deal with fonts and other embedded textual features) whatever encoding that caused the history issue is gone and you can use the page with history as you had previously been able to do.