VBScript to open Excel file with *.xlsx extension

I'm using VBScript to open an Excel file with an *.xlsx extension.


Set objExcel = WScript.CreateObject ("Excel.Application")
objExcel.Visible = false
Set objWb = objExcel.WorkBooks.open("C:\filefolder\filename.xlsx")

I'm getting the error "Excel cannot open the file...because the file format or file extension is not valid."

If I change the format of the Excel file to Excel 2003 (*.xls") the file opens successfully. I have a number of files in xlsx format to open and I don't want to change the extension on these files (other people have access to these files). Any suggestions? I've scoured the internet for solutions and have come up empty.