Mac Mini won't Boot

[mikethebook]

I have a 2009 Mac Mini running El Capitan off a 250GN SSD drive and suddenly it won't boot. The Apple logo appears and the progress bar runs about half way before the light goes out on the computer and it shuts down. Safe Mode doesn't appear to work either. Running Disk Utility repairs from the Recovery Drive doesn't work suggesting an error beyond fixing but I tried running Drive Genius and it suggested all was well with the drive including Boot Camp which still runs. With a house move coming up I really don't want to do a clean install right now. Is it worth reinstalling the operating system without changing the files or is the problem likely to be something else. I notice that I can boot into my Carbon Copy Cloner drive but it works incredibly slowly-I can't open up Chrome-I did a fresh clone yesterday before doing a regular Onyx clean but it all went pear-shaped today when trying to reformat an external drive. But if the CCC clone worked so badly then maybe there was something wrong then. Any suggestions would be much appreciated . . . but it may come down to a clean install.