Incorrect User
If the missed call icon shows constantly it is because taskbar notifier does not have access to the correct preferences files. This is caused if your home directory is returned incorrectly.
On a 1.1.3 or above phone the applications should run as mobile. This is what mobilephone.app runs as and unless Taskbar Notifier is also running as mobile it cannot access the files it needs.
On a pre-1.1.3 phone applications should run as root.
To resolve this problem you should edit the value of the key 'UserName' in the file com.JC.SMST.plist. That is 'root' for pre 1.1.3 and 'mobile' for 1.1.3 and above.