I usually use this to open large flat files.
http://www.portablefreeware.com/?id=693
You should look at the errors to find your problem. Those will help you identify the row that's missing.
Are you sure that you're missing a row?
Could it be that you're counting an empty row at the end of the file?
Are you using a data flow task? or something else?
Could you use an error handler?