Since we are talking Now Up-to-Date data, it is probably not corrupted, just having a problem recognizing something on the import. If you open the data file in a text editor, look for an event that ends at or crosses over midnight(00:00). If you change the end time to 23:59 it should then be able to import.

Now Up-to-Date has a problem importing when it thinks an event crosses over to another day. This can, occasionally, appear this way even when the data came from Now Up-to-Date on an export.
Don Norcross
Technical Support - Now Software Inc