Thanks John - that is a very sage advice - I actually wrote bunch of wrapper function for some typical tasks (save as CSV, apply changes and save, apply formatting and save, add comments and save) and I constantly struggle with some degree of unpredictibility. Call that are fine if made once fail on subsequent invocation etc.
It is possible that the culprit is reusing of Excel object:
    # use existing instance if Excel is already running
    unless (defined $excel)
    {
        eval 
        {
            $excel = Win32::OLE->GetActiveObject('Excel.Application')
        };
        die "Excel not installed" if $@;
    }
    
    unless (defined $excel) 
    {
        $excel = Win32::OLE->new('Excel.Application', 'Quit')
                or die "Oops, cannot start Excel";
    }
    #to avoid excessive dialogs when saving in non-Excel format
    $excel->{DisplayAlerts} = 0;

[download]
If I understand you correctly I should always use: 
my $excel = Win32::OLE->new('Excel.Application', 'Quit')
                or die "Oops, cannot start Excel";

[download]
Is that correct?
I typically add: 
    $excel->Quit();
    undef $excel;

[download]
at the end of any function. Shouldn't it take care or Excel objects?

In reply to Re^2: Win32-OLE: What is the canonical way to open file for editing? by woland99
in thread Win32-OLE: What is the canonical way to open file for editing? by woland99

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