Last night, I was browsing with safari, e-mailing with the e-mail programme and altering a spreadsheet in numbers. After that, the tilt lock kept coming on and going off automatically every 30 seconds or so. The machine also started working very slowly. When the lock was off, it would take 10-20 seconds to rotate to portrait (and visa versa) then the lock would come back on. Pressing the button seemed to take an age to go back to the home screen (sometimes the button would not work at all) Anyone any ideas? Thanks in advance.