I reported a couple of days ago that ZoneAlarm Antivirus protects itself against CCleaner's attempts to remove its log file (C:\Windows\Internet Logs\ZAlog.txt in Windows XP). ZA Pro and ZA Security Suite do this also. It is also true of ZA Free. All of these defenses seem to have appeard in the latest versions 6.0.667.000 of these products.
Unlike its more costly brethren, ZA Free does not signal what is going on, but the file does not disappear. There is a now an option under Overview | Preferences that is checked by default: "Protect the ZoneAlarm client".
The protection does not extend to old logs, however, nor to tvDebug.log.