is the error 1004? (Try even if it is just the generic error too..)
If so read this....
and if that does not work.. read this...
and if that doesnt work read this...
Some of the files listed in the above link may have changed locations in Mav and ML.. so use something like FindAnyFile to locate them.... if you cnanot locate them manually.
Thanks, Art. Tried all those things, but didn't fix it. Think I'll bring this home and work on it there. It's at school now, and there are proxy servers and crap here that MAY be getting in the way. Can always restore from a 3-week old Superduper clone, though I'm always a bit worried about how that will affect syncing of documents and stuff in my Dropbox and iCloud stuff. I do have other macs, so this isn't critical. Anyway, thanks for your thoughtful reply.
Just got back to my Mac. To respond to Mr Art of Sound, "no" there is no error code or any instruction on what to do next, it merely seems to hang stating there was an error, and i cannot get rid of it to start again. I assume that the links providde by Art of Sound only pertain to an error 1004???
It gave up with just one minute to go, that after five hours of download!
No.. the generic error issue you speak of, can also be fixed by one of those solutions i posted.... Its a fairly common problem and sometimes you get just an error msg and sometimes you will get the 1004 error code.. They basically mean the same thing in terms of possibile solution... and are most often caused by a break in or issue with.. your net connection resulting in an incomplete download that for some reason, trips up the process built into OS X... so it cannot resume as normal.
Glad to hear you took the time to make and have a clone image to restore from.... If only others were so diligent as it would save them so much hassle if/when things go wrong...