my 18month old 27 inch iMac, has developed a couple of problems in the last week or so. Firstly the brightness level (overall) is intermittently dropping down. Its like its about to hibernate/sleep, but doesn't. It often does this while typing or using the computer in some way. It stays at a lower level for a few seconds normally, then back up to normal brightness, The second issue is again intermittent (the worst type of fault!) In that the left had side of the monitor intermittently goes darker. THIS DOESNT rectify itself, until the mouse is moved or clicked. Approximately half of the screen is effected by this. Anybody any experience of this, (or similar) happening? I assume the warranty is 12 months in the UK.