Well i have a powerbook G4 and my system seems to have been partially messed up.
Suddenly all apps in the app folder got erased. Repairing permissions did nothing. So I copied some of the apps from a backup folder I had, and some from another computer. Also redid the 10.4.11 update. Some of the restored apps work. Others like Mail and my HP printer apps die. Mail only dies when it tries to go get new messages. Ugh. Went to the "genius" bar and they tried a deeper permissions repair. But to no avail. They suggested reinstalling the system via archive and install. I sort of thot that I should try to get tiger working before trying to upgrade to leopard. Also I can't find the original tiger install discs. SL of course is not compatible.
Ok, so you still have a backup? Make duplicate full backups if possible.
If i were you, i'd get a hold on a leopard disc and then erase and install on the internal drive (disconnect your backup to make sure), then i'd install all the apps of the web or install discs (including iLife (might be worth it to grab a leopard mac box set)) and then drag and drop your files over from the backup. Change all the settings to your liking manually and copy files over from the "application support" folders were needed - keep this minimal as your problem is with the applications eg: your email mailboxes are in user/library/mail/mailboxes.
Hope this helps.
JUST DON"T FORGET TO BACKUP!
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