Access 97-Un-installable ISAM Error

I have encountered a problem that effects about 2% of our ACCESS application users (approx. 6 out of 300 users throughout the US).
They use Access version 97 SR-2 and run an .MDB application for generating Access reports which work fine. However,there is a selection button in the program that provides them with a Excel file of a data dump of all the info. in the reports.
When these 6 people select the Excel Spreadsheet button in the reports they get an “Un-Installable ISAM file” error whentrying to create the Excel file. I can not find any one who has a suggestion on how to resolve this error. Can you point me in the right direction?
Thanks, Jim