Yes... I've saved queries, only to have them error out when I run them... usually cuz of something I did incorrectly and saved without testing first.
Nope, can't say I've ever saved one, opened it only to find it completely different from what I created.
Is this on the same machine you had your previous problem on?
Access doesn't work that way. Windows doesn't work that way.... Basic DOS does not work that way. (Linux doesn't work that way either). Hardware malfunctions DO however, cause things like that... usually bad memory, but I would think that you would be getting some sort of indication of a problem outside of simply creating a query only to find it didn't save as you wrote it.