I am getting a "Failed to process the report" error message when trying to preview a report in an excel format in Report Designer. This is puzzling because
1) I am able to preview the report in an excel format for different customers (other than the one the report is being run for).
2) I am able to preview the report in html format.
3) I am able to preview the report for the customer in question if I generate the report for each line item on the report. There are 26 line items on the report and the preview works if I run the report with only one line item at a time. I have also been successful in getting the preview in excel to work if I run it for 3 or 4 line items at a time. However, it doesn't work if I don't restrict the number of line items and run it for the full 26 line items.
4) When previewing the report for different customers (than the one for this report), there is no issue with the number of line items. Many have 100 + line items.
5) The report has worked fine for the customer in question for the last 8 weeks. It just won't work with today's data. It will probably work tomorrow.

What would cause this inability to generate this report today? If it works for individual line items, why won't it work when it is un-restricted? Is this a bug or am I doing something wrong?