We are having the same problem. Specifically, the problem occurs on this page:
http://wiki.earlyimpact.com/how_to
It only started occurring in the last 30 days or so. The page reverts back to a previous version, but the code on the page is not complete. So it's a previous version of the page, minus some of the content (syntax) at the bottom of the txt file. This has happened now many times on this page, and it always goes back to the same, exact state.
We are ruling out that this could be a malicious user.
We have the WIKI setup to notify a certain e-mail address of any edits made to it, but no notifications are sent when this occurs.
From what we can tell, this behavior may be due to a bug. We just updated to the latest version today and we will keep monitoring the problem. We will post back here to indicate whether this bug appears fixed in the latest version or not.