The file is valid. I can open in Excel on a local machine without an issue.
I receive the error in the "Excel Source Editor" when clicking on "Columns". Also, the "Name of the Excel sheet" drop down results in "No tables or views could be loaded".
Try these two things and post what happens:
1. Delete the Excel file connector, then delete and recreate the Excel source file in the directory it is being read from with a differant name, then create the excel file connector again pointed to the new file.
2. Open the Excel source in the data flow task and select query as the source instead of Sheet. Use the Query editor to see if you can add the sheet and select all columns from it.
This will take care of any issues that might occur if your source file became locked, cached in memory, sheet renamed or ouyt of order etc...
It might also change your error just enough to get a better idea of what is going on.