Okay so when I updated my phone to 1.1.3 my summerboard icon was lost. Here is what I did to fix it:
1. First backup then edit the private/var/mobile/Library/Installer/LocalPackages.plist file to remove the summerboard program. just remove everything from the first <dict> to the last </dict> for summerboard only.
2. Backup then edit system>Libary>Core Services>systemversion.plist to change the version number from 1.1.3 to 1.1.2.
3. Restart phone then install summerboard again.
You should now be good to go!