I am working with Excel 97 for a long time, and have never seen this.
What if you call it like:
oExcel.Application.Workbooks.open(".....")

Also try to check first for oExcel state (for more details see discussion thread #771427)

>All,
>
> I have a client with Excel 97 running on a machine. My VFP program opens a workbook, but when the code runs I get a workbooks does not evaluate to an object. The code(below) works with Excel 2000 and XP. What's wrong?
>
>

>    oExcel = Createobject("Excel.application")
>    oExcel.workbooks.open(".....")
>