DataManager will check files once it downloads and report if it finds a problem. Removing DataManager doesn't remove the data. A file may have been corrupted during download. Try deleting the data on the computer and re-download. Here's how on Windows 7.
first make hidden folders visible.
open the 'folder options' control panel
click on the 'view' tab
select 'show hidden files, folders, and drives'
stop datamanger from running
press control alt delete keys
select 'task manager'
select the 'processes' tab
click the 'end process' button.
click 'end process' again.
click the x to close window
now delete the data
delete all the files inside 'DataManger' folder
C:\Users\<your name>\AppData\Roaming\Seattle Avionics\DataManager
Now that the data has been deleted, restart datamanager and click 'download' button.