Can't get to login screen

"Darwin User-1s-iMac.local 10.4.0 Darwin Kernel Version 10.4.0: Fri Apr 23 18:28:53 PDT 2010; root:xnu-1504.7.4~1/RELEASE_I386 i386"

On boot, I see the blue screen (differing shades) forever. I can ssh in, and I see looping messages:
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Nov 28 17:46:14 User-1s-iMac loginwindow[6059]: Could not allocate LoginAuthRefMgr instance.
Nov 28 17:46:14 User-1s-iMac com.apple.loginwindow[6059]: Could not allocate LoginAuthRefMgr instance.
Nov 28 17:46:14 User-1s-iMac loginwindow[6059]: Login Window Started Security Agent
Nov 28 17:46:14 User-1s-iMac loginwindow[6059]: Login Window - Returned from Security Agent
Nov 28 17:46:14 User-1s-iMac loginwindow[6059]: AuthorizationRef doesn't have a username ((null)). Exiting.
Nov 28 17:46:14 User-1s-iMac com.apple.loginwindow[6059]: AuthorizationRef doesn't have a username ((null)). Exiting.
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Single user mode works. fsck comes up clean.

From what I've researched, I need to rebuild netinfo. Except that I don't have netinfo in Snow Leopard. So, what do I do?

Thanks!

P.S. The user I installed doesn't show up (short or long name) is /etc/passwd. Is that significant?

More drivel: before the last reboot, computer was going very slowly. Top showed Dock ⚠ spinning 100% of the CPU.