For what it's worth, this has happened to us twice separately on production web sites. For whatever reason, a file gets write locked, then Kentico doesn't finish writing it out correctly. Then the Web Analytics scheduler job fails on that file. It throws an exception and stops processing. Then, when the scheduler runs the next time, it loads the file first, same thing. The other files start backing up since they are never getting processed.

You (Kentico) really need to change the code so it simply logs if a log file is broken or can't be accessed, and continue processing the other files. Otherwise, if the admin isn't watching closely, you get 10,000 log files filling the directory in no time at all since Kentico creates and deletes gobs of these log files every minute it seems.