continuation from previous post here.

We’ve tried several things to solve the problem including downloading the combo updates directly of both 10.6.5 and 10.6.6 and install without using software update. We’ve tried increasing the kern file size allocation in terminal. We’ve repaired permissions. We haven’t tried running the update from another computer onto the target computer but you’d need me in the home to do that. So here’s what we have left that you can do yourself...

I hate to have to punt but this may be our only choice. I would suggest one of two steps.  Either a: wait for 10.6.7 to be released (next few weeks) and hope that 10.6.7 will update but it's doubtful.  Or b:  reinstall Snow Leopard from the disc then run the updates once again after installation.  You won't loose any of your data as Snow Leopard will only replace the System and not your user data.  However you just definitely be sure you've backed up first.  Time Machine should be running before you do this.  And it probably has been.  Right?