After setting the "Ignore Other Applications" checkbox on the General tab of
Tools-Options, I get "Personal.xls locked for editing" when double-clicking
to open another spreadsheet. After clicking on the Read Only button of this
popup, the other spreadsheet correctly shows up.

After I close these workbooks out without saving I try to open again with a
double-click but get a popup which says it either can't find the spreadsheet
itself or one of its components and after clicking OK I get no workbook
showing at all.

If I then close this and just open excel with a blank workbook, uncheck the
"Ignore Other Applications" and close, all is well again.

It would appear then that "Ignore Other Applications" is persistent and
probably "stored" in personal.xls. But it might be nicer if this was
automatically unchecked when the last excel is closed.

Ken Shaffer