Every time my iMac is shutdown or restarted, all my web and mail
preferences are lost in the Internet System Prefs Panel. I have tried
trashing preference files from ~/Library/Preferences but nothing seems
to work.

I am running OS 10.2.6 on a 500 mhz iMac with the RAM maxed out at 1
gb. My hard drive is only about 1/4 filled. All suggestions