Need urgent advice please - my 14 days to return is almost up. Love my new i7 27" but it has an odd random tick or click sound. Hard to reproduce it reliably, but more often than not is when a new safari page is opened or the screen saver comes on. Sometimes it happens when I open a file. Fan is dead silent. Apple phone support have no idea about this. It is not very loud and sounds like an electrical switch is going on/off or opening/closing. I switched off any electrical gear nearby (ethernet hub, modem, Time Machine back up, external speakers) and it is definitely coming from the iMac. Has anyone else experienced this? Any ideas what it might be? I hope I don't have to have to return it - I've had a fair bit of grief setting it up from a clean install. All help appreciated.