eMac sleep won't wake up

When my eMac goes to sleep, it won't come back from a black screen. If I restart, it comes up ok, but when it times out, it won't wake again. If I go to the preferences panel and select screensaver, the pref panel crashes. Another oddity, the titlebar clock stops at 3:01 Friday. The control panel clock keeps running, and sometime over the weekend, it fixes itself and Monday AM when I come in the titlebar clock is ok again.
Any ideas?