Task: Question Answering
Input (English): I recently downloaded Firefox 3 , and it worked fine . this morning when I opened it , all my bookmarks were gone , and I couldn't use the forward and back buttons ; they were grayed out . I went into my Norton security and told it to allow Firefox , and I restarted it and it was back to normal . I closed it , re - opened it , and its messed up again ! 
Question: What may be causing Firefox to mess up ?
Output (English): My antivirus program isn't letting it run .