Hi Theandor,
Thanks for the further information. What you are describing sounds odd and not what you should expect. Is there a set of steps (including symbol name, date range, export type - eg. ticks) that you are getting the issue with? The only thing I can think of that you should check is that the export process hasn't terminated prematurely (any error should be in the log window). The most likely issue would be running out of disk space.
When you say that Notepad++ cannot "identify" it, what does that mean? Notepad should be able to read in any text file, regardless of format. The only reason it should give an error is if you are out of disk space and/or the file is locked/being written to.
Thanks.