Option setting mysteriously changes

In an Excel 2003 workbook I have now on 4 occasions over about 5 years of usage found that the radio button for Objects on the Tools-->Options ( General Tab ) has mysteriously changed to "Hide All" instead of "Show All". Interestingly, instead of just hiding the objects in the workbook (that I have macro's attached to), it also disables the displaying of the data validation drop down lists across the entire workbook.

Is there some short-cut key sequence that I might be accidentally entering that causes this setting to change? Or is there something I might be doing in editing my objects or the macro's associated with them that causes this change? Or is there something in editing or adding data validation that I might be doing?

The seemingly undocumented disabling of the drop down list and its control by this "Objects" setting is surprising. I discovered it by accident.

I develop and maintain the workbook on one machine and send it for production usage to another. I seem to discover the problem only on the production machine. I assume the Option settings are a part of each workbook, not tied to a machine. I don't know if this has any bearing.

Originally Posted by Paul

I usually give the user a raised eyebrow look and think "Ok, what did you do to cause this?". Rarely do I actually say it, just think it.

my conversations usually start with me saying "what did you do" and ends with me leaving shaking my head and wondering how this became my problem.

I like my errors nice and consistent and easily replicatable. i dread the helldesk call from a user that sarts off with "well sometimes its just goes kind of funny!!" FFS

As for a solution to this problem, i fear im no help, and wandering off topic.