.visible property causing an error in Excel 97
 

I have a macro that blows up when any properties of a worksheet is referenced. When I view the watch window I can see that the current workbook is active and I can view all the properties of the worksheet. When I step into the line "If ActiveWorkbook.Worksheets("worksheet name").Visible = False Then"
it blows up.

The error is 'The instruction at "0x651b41d3" referenced memory at "0x0000004xc". The memory could not be read'.

Sometimes I can step through this error.
The error does not occur when mso9.dll is referenced but this dll is not present on all machines.

Any suggestions?