I have a problem with the keychain not allowing access for password to login

I have a late 2009 iMac, Intel Core 2 Duo Processor 2.66 GHz, Memory 8 GB, Bus 1.07 GHz. I am running current Yosemite.

Since the Yosemite upgrade I had many small problems, requiring constant verify and repair permissions. This week had to repair disk before the verify would run. The next day I boot up, type password, it is accepted, then the login gear wheel will not complete the log in. I tried my wifes' login - same thing. After trying all the restarts I know of, I had to call Apple for help.

After talking with two Advisors, the only solution they could think of was a disk wipe and reinstall. I have an external backup

but, due to circumstances, a large amount of critical information has not been backed up. I hope some one here knows of

any way to avoid such a setback for us. I had one idea but don't know if it can be done, and that is have some one put their

computer in target mode and rescue our files from there? The log reports has the same few lines each time the login fails:

OSIESpringboard[404]:cannot connect to / var/run/systemkeychainecheck.socket: no such file or directory.

Failed to unlock keychain/

OSIESpringboard[404]: GetDVLDEntryPopintWithImage.

I Thank you for any help you can give.

Truitt