Hi All. First of all, I must confess that I am a PC user (please be gentle/patient/detailed in replying). However, I happen to work in a lab that uses MACs and am having quite some trouble with our G4 (as this is the only computer of any power for ~9 people, this poses quite a problem at times). In any case, for some reason the computer screen will flicker (almost like it's "blinking") several times and, more often than not, the system will freeze, requiring it to be reset. This is a chronic, recurring problem (to the point that people save their work every minute or so). I really have no idea what is going on (having never encountered such a situation before; my initial thoughts are bad HDD and/or RAM) and am rather hoping that you may be able to help. Many thanks in advance. Take care.