I have a PowerMac G4, AGP model. I connect one external hard drive and one external DVD writer to my computer through the two built-in firewire ports. However, the computer mount any of my firewire devices on the afternoon (they still working fine on the morning). I had try three way to fix this problem. I did try reinstall the external devices, I did try un-plug every thing include the power of the computer and reconnect them back, and I also reinstall my OSX. However, all three ways still not fix that problem. Both of my external hard drive and DVD writer have USB port. I did try to connect them with the USB, and they work find. So my question is does this problem cause to the firewire port or the mother board of the computer (I don't think this problem is cause by my devices because they still work with USB). How can I find out which part cause this problem? And also how can I fix? Thank you very much.