The following error message, or similar, indicates that your history file is corrupt on a specific line.

Start analyze log file: ex090202.log
Error: History file “D:/home/<username>/stats/history/??????.txt” is corrupted (in section UNKNOWNREFERER). Last line read is number ???.
Correct this line, restore a recent backup of this file, or remove it (data for this month will be lost).
End analyze log file: ex??????.log

To fix the problem you will need to edit the history file indicated in the above error message and modify the line also indicated in the same error message before updating your stats again. This can be performed from your MyCP’s file manager or by using FTP to download and re-upload the history file. If you are unable to fix the history file yourself or if it claim more line numbers are corrupt, please open a support ticket and paste the error message into the body of the ticket.