This is me: http://forums.macrumors.com/threads...s-after-restart-reboot.1883716/#post-21372162 [tl;dr: My iMac (mid-2011, now running El Capitan) runs fine for a while and then, with no consistent/detectable preceding stimulus, beachballs, although my mouse cursor (usually) still moves and the clock in the menubar (usually) continues to run. Everything else locks up.] Everything I have already tried, at the suggestion of several helpful MacRumors members, is in that thread. In the nine months since that post, I have: Restored my Mac, via Time Machine, to multiple restart points; Wiped and reinstalled twice, including (on the second reinstall) downloading every app and manually restoring every preference while restoring from Time Machine/Crashplan only the most idiosyncratic (personal) files. Upgraded, one step at a time, to every OS X version from Mountain Lion to El Capitan. Gotten really frustrated and, for weeks at a time, lived in Windows 7 on my Boot Camp partition. After every reinstallation/upgrade/long period of OS X disuse, I am able to use my Mac for a few days, sometimes even a few weeks . . . until the beachball returns, and after reboot(s) returns at increasingly shorter intervals until I perform another attempt to salvage my system. I am now out of things to try. The idea that it is a hardware issue is possible, but seems unlikely, because during those intervals, I use the Boot Camp portion of my HD without error for weeks at a time. (I also did several hardware tests as noted in the previous thread, including the AHT, memtest, and several dozen Disk Utility verifications/permissions repairs, etc.) The reason I have not taken my iMac in for service is because of the delays involved: I need a machine daily, and it is likely that any given time anyone would boot my Mac to service it, it would work fine for quite a while before manifesting its affection for beachballs. And any actions taken to fix it would (I fear) result in an apparently successful, but (upon return to me) merely temporary cessation of beachballs, and my Mac would be on a shuttle back and forth to the service shop. I am at a point now where I am considering giving up. I would buy a new iMac (it’s coming up to time --five years -- when I would anyway) but I have little confidence that (I am just guessing here) whatever particular constellation of apps/preferences/bad karma I have that is causing this problem won't avoid beachball syndrome on a new system restored with my present data. And I would be $1k-2k further into my problem. I am asking for any and all suggestions. They will be greatly appreciated.