Hi. I'v noticed from time to time, that my MBA is slowing down a bit, mouse is not responding for a few seconds, dock is really slow etc. Launched Activity Monitor and the CPU usage was a bit high for one of the processes: mdsworker (60-80%), which gave me the famous core shutdowns after a while. And bang, there it was. Did a bit of research and found, that this is Spotlight indexing process... which is indexing my Downloads folder, while downloading something. So for anyone having the same issue, it will help a lot, there is the solution for that: 1. Set every single download (from Safari, Firefox, Transmission, Skype etc, whatever you use) to one download folder.* 2. In System Preferences, under Personal, go to Spotlight. Select Privacy tab and add a folder, your download folder to the list. * Setting all of them to one folder is easier, but if you prefer to keep it separated, in step 2 add all of them to the list. This will stop endless indexing of downloaded files. Thought I had this set, but apparently not. This helped me a lot. Hope it will help you too.