Some general guidance:
1. When dealing with import file issues, the best example to offer is a sample of the file itself. This should be archived if possible, to prevent any inadvertent modification of the file contents.
2. Data on the source of the file should include the application used to generate the content and the export method and settings used to output the file.
In general, my experience has been that CSV outputs from Excel are problematic, in that the content may be escaped in unexpected ways that cause the parsing code to lose synchronization with the field contents (ie "it gets confused"). Once this happens its rather hard to get more specific than "data is empty or corrupted". This can often be worked around by using a tab delimited format - which seems to have fewer problems. Your mileage may vary on this - there are a lot of environmental variables involved..
David