This issue has occurred for some customers who are also using BitDefender antivirus for IMail.
There are two methods you may use to resolve this problem:
1) Run the Bitdefender installer in a repair mode and then reboot the server.
2) Download the full installer for HF1 from myipswitch.com and run it in repair mode. (Note: This technique may also require a server reboot).
If queue manager will still not stay running after using these methods, you can temporarily disable BitDefender and restart the queue manager service to allow mail delivery. In this case, please contact Support for further assistance.