Can't read input Excel file in Management Reporter

After migrating all my FRx reports to Management Reporter, I find that I can't run any that use Excel worksheets as input. When I run the reports, the following message appears in the Report Queue Status window:

ReportProcessor.InvalidWorksheetFileReference

I tried re-linking to the Excel file, but I had several problems:

1) If I left the link the way it was in FRx and tried to resave it, I got an error: 'The worksheet file must have an .xls or .xlsx extension'. This is the way it was formatted:

\\hda05\great plains shared\FRx worksheets\[LOGPFISUNITS2011.xls]Sheet1

The only way to get rid of the message was to format it like this:

\\hda05\great plains shared\FRx worksheets\[LOGPFISUNITS2011]Sheet1.xls

...but then I get the first error.

I also tried replacing the \\hda05 with a mapped drive letter, but that didn't change anything.