I seem to be in a catch 22 loop with my attempt to install latest OS update on my mac mini. I got a sort of uninformative frozen screen, just an apple and a frozen progress bar with no time estimate for download. I waited a couple days then tried installing the OS in recovery mode. It looked better at first, but then changed to that same frozen progress bar with not time estimate. I tried restoring from a time machine backup but got the message that I had to install the OS update first. And when I try to do that the same thing happens--frozen progress bar of death. I really need to get my machine functional again. I don't understand why what seemed like a minor update to the OS has apparently wrecked my machine. I ran disk utility and got no complaints on the drive. I fear I've screwed things up. Suggestions please? And thank you.