Hi -- with this particular app there can be many causes...
The first thing to eliminate is Virus/Malware-- because many do utilize this function once you are infected.
I know you have Zone Alarm running... but no software is absolutely perfect defensive barrier. New bugs happen every few seconds, unfortunately.
I suggest you follow the Prework link in my sig-- and post a HiJack This log in the
HJT log forum for analysis.