My old PC nearly died one time due to the fan being clogged w/ dust. Since then my routine was to vacuum the fan once a week and it worked well. Yesterday I did the same w/ my new iMac and I must've hit a button on the keyboard or something as it went dead and I had to power off/on. The keyboard's green light was flashing. Probably should've at least turned off the keyboard. Wonder what I hit? Is it safe to vacuum while on?