Recently, sometimes (rarely) when we export data from our application, the export log contains float values that look like "-1.#J". I haven't been able to reproduce it so I don't know what the float looks like in binary, or how Visual Studio displays it. I tried looking at the source code for printf, but didn't find anything (not 100% sure I looked at the right version though...). I've tried googling but google throws away any #, it seems. And I can't find any lists of float errors.
See also: stackoverflow.com/questions/5541975/what-does-1-mean/…