imac g3 keyboard not working on boot

I have a 500mhz slot loading G3. After the computer has been sitting, if it is turned on, the keyboard (and other USB devices) will not work. If it is unplugged, it all starts to work. If I restart it, the keyboard works. If I turn it off and then turn it back on, it works. If a device other than the keyboard is plugged in directly, they work no matter what. I swapped keyboards to the same result.

What is going on here? Any fixes for this sort of thing?

Hmm..im encountering that same problem. With my Mac Pro. my Mouse works..but the keyboard doesnt on it..but when i plug it into my imacG5 my keyboard works fine there..but not on the macpro. Im guessing theres a faulty connection..im not really sure whats happened either?