HELP!! login problems on 10.6

Ok, I have a 20" iMac only a few months old, running 10.6 Snow Leopard. Everything worked fine last night and I didn't do any system updates or install any software, but when i got home from work, I tried to login and it would not allow it, just the shakes. I usually have a "guest" account with no password, but when I looked for that, it was gone.

Here's what I've done so far:
1. Tried every password I've ever used for login...nothing but shakes
2. Booted with DVD and used password utility to change password for my account...nothing but shakes
3. Booted with DVD and ran disk utility to verify the hard drive...ERRORS.
3b. Ran repair disk...still errors
3c. Erased disk and reinstalled from time capsule backup....nothing but shakes at login.
4. Booted with DVD to rerun disk utility...no errors.
4b. Changed password...nothing but shakes

So, now what? I really don't want to go thru another reinstall process to a fresh operating system and try to recover stuff from the time capsule. Is there anyway to get in there?

 

Thanks for the reply, I tried the single user mode two separate times and still get the shakes...now, I'm worried. I'm going to just go ahead and do fresh load of OSX and see if I can just get it to boot up and worry about my files later.

 

There is no option to change the login name, just my picture with the name beside it and a block for the password.

I even tried just reloading OSX without erasing the drive...no joy, time to start from scratch.

If anyone has any ideas what happened, I'd love to hear them to prevent this in the future.