Help..haven't been on here for ages because everything has been working fine. However my iMac is now misbehaving. Everything I do when I click it seems to hiccup and have to think about springing into action...the little coloured wheel goes round. Even typing in emails and forums sometimes there seems to be 'stop' then suddenly the letters appear secs after I've typed them. Also I've noticed that whatever I ask the mac to do the external springs into action..is this normal? There is masses of room on my HD. I have an external HD of 1TB. I have done a virus scan and nothing. Any idea's? Apologies for writing this so untechnically but I just switch it on and off, I don't understand how it works. Thanks for any help or do you suggest I ring Apple support?