If you get an "Ole::Storage::FormatError: OLE2 signature is invalid" error when reading an Excel spreadsheet using Roo it can probably be solved by resaving the spreadsheet (unfortunately using Excel) and making sure it is saving it as "Microsoft Office Excel Workbook (*.xls)", etc and not something odd.

I had two spreadsheets that had the .xls extension, but seems they were masquerading; when doing a Save As on them one was actually in a "Text (tab delimited)" format and the other in a "Web Page" HTML format. These were system generated files, so I guess that explains their odd form.

Couldn't find a whole lot of help out there about this.