It was fine with pre 3.2 releases but ever since it has been a nightmare. I have seen reinstalling an older version and overwritting with the new version "sometimes" will help.
A quick workaround is to disable ZoneAlarm for few minutes, run Offline Explorer, go to the Options dialog and uncheck the Internal HTTP server box. Click OK button to save the change. Now you can enable ZoneAlarm again.
We already contacted ZoneAlarm support about this problem. We hope that they will fix it soon. ZoneAlarm 4.5 and earlier versions didn`t have this kind of problem.
If this is not the Zone Alarm issue, please let me know.