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My Help Viewer also crashes when I try to customize the toolbar in Panther. I do have the search box in Safari and Finder Help though.
You won't get a response from Apple by submitting a bug report...so don't hold your breath.
You can try a couple of things to remedy this:
1. Create another user account, login, and see if it does the same thing.
2. Delete the following file located in Macintosh HD > Users > yourname > Library > Preferences:
com.apple.helpviewer.plist
3. Run Disk Utility and Repair Disk Permissions on your startup drive.
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