I have no trouble with control panels on my Yikes 400, but I did have the problem with the modem dialling out repeatedly when I didn't need it to, including on startup.
The fix was to trash ALL the Preference files. I never found out which one was to blame, and because this happened very early after installing Mac OS 9, I wasn't losing anything important. Removing the Preferences folder from the System Folder stopped the problem dead, though.