[Update: Changing the user ID (App Store / Mobile Me) will also cause this issue, use ONE login on your device. -Perhaps a shared one; keep the password secret for billing purposes...more here]
you'll need a Secure SHell to the iPhone.
(SSH should be among the first few programs installed, with BSD subsystem (necessary for most programs) , and BossPrefs (necessary to turn SSH on and OFF when not needed.))
Insure WiFi is enabled.
Insure SSH is On (if you were able to turn it off).
Goto 'Settings', select 'Wi-Fi', and press the little arrow to the right of your wireless network name.
Note the your IP address.
If using Cyberduck, Click 'Open Connection', enter your IP address into the server field.
Enter root into the Username field.
Enter alpine into the password field (unless you changed it).
click 'Connect' -[allow up to 30 secs for secure key generation if SSH wasn't used before.]
[Select /private/var from the pull-down menu, and click double-click 'Library', then double-click 'Installer' from the resulting lists.
** private/var/root/Library/Installer directory if apps weren't relocated from the 300MB partition.
[Note: I've found just deleting the 'RemotePackages.plist' file works.]
(These will be recreated by Installer.)
Do *not* delete the 'LocalPackages.plist', as this contains all your installed packages.
Reboot the iPhone.
Before turning OFF Wi-Fi & SSH (see end of this post), check to verify Installer loads.
I'll wait here....
Time to reinstall the 'Installer' application:
Run 'Terminal' from your 'Utilities' folder.
Enter the following:
ssh root@your IP address
when prompted, enter alpine (or your password)
Enter [Case-sensitive]: (or copy/paste)
rm -rf Installer.app
chmod +s Installer.app/Installer
chown -R root:wheel Installer.app
Be patient, after your iPhone completes the reinstall, type exit to end the session.
Reboot the iPhone.
Upgrade to the newer version of Installer if prompted.
Don't forget to turn OFF SSH (install 'BossPrefs' if necessary)
[ installer repository: sleepers.net/iphonerepo ]