I have read this one as well. I think they should try to disable there Norton Anti virus and changed it into another anti virus software.
By the way here is the e-mail of pegasus chairman
Since a signature update on May 15, Norton Antivirus has begun detecting the Pegasus Mail executable program, WINPM-32.EXE as a trojan horse called â€œTrojan.Dropperâ€. The first symptom most people will have of this problem is the deletion of WINPM-32.EXE during a system scan.
Firstly, we wish to stress that there is no trojan horse in Pegasus Mail: the Norton Antivirus program is producing a â€œfalse positiveâ€ - an incorrect analysis based on poor or erroneous signature information.
Secondly, you will not be able to recover from this problem without first amending your Norton Antivirus installation, since it will automatically delete any attempt to download or reinstall the Pegasus Mail program.