The following demonstrates that a macro behaves differently if the shortcut
key assigned is UPPER CASE than if the shortcut key assigned is lower case.

o Create four new blank workbooks: c:\temp\a.xls, c:\temp\b.xls,
c:\temp\c.xls, and c:\temp\d.xls
O Put an "a" in cell A1 of workbook a.xls, a "b" in cell A1 of workbook
b.xls, etc.
o In workbook a.xls create two macros as follows:

Sub open_them()
Workbooks.Open Filename:="c:\temp\b.xls"
MsgBox "Opened b.xls"
Workbooks.Open Filename:="c:\temp\c.xls"
MsgBox "Opened c.xls"
Workbooks.Open Filename:="c:\temp\d.xls"
MsgBox "Opened d.xls"
End Sub

Sub close_them()
Windows("b.xls").Activate
ActiveWindow.Close
Windows("c.xls").Activate
ActiveWindow.Close
Windows("d.xls").Activate
ActiveWindow.Close
End Sub

o Assign shortcut key (Tools/Macro/Macros/Options) o (Ctrl+o) to open_them
and c (Ctrl+c) to close_them in workbook a.xls.

o Enter Ctrl+o in workbook a.xls. Click OK to acknowledge the MsgBox for
each of b,c, and d.
The three workbooks b,c, and d are opened as expected.
o Enter Ctrl+c in workbook a.xls to close the auxiliary workbooks b,c, and d.

O Reassign the shortcut key for open_them in workbook a.xls to O (capital
letter O) (Ctrl+Shift+o)
o Enter Ctrl+Shift+o in workbook a.xls. The macro opens workbook b.xls and
proceeds no further.
Neither the MsgBox statement for "Opened b.xls" is displayed nor are
workbooks c.xls or d.xls opened.

o The above sequence fails regardless of what letters are assigned. Any
upper case letter assigned to open_them fails as above.

The problem is easily avoided by not using upper case letters for macro
shortcut keys but is rather perplexing until the cause is identified. I had
recovered/repaired/reinstalled several workbooks and Excel before isolating
the difficulty.
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