Can’t log into admin panel after 6.5 upgrade

Okay, I have been scouring these forums for a fix on this one. There is a lot of information about this bug. However, after following all instructions that I can find here … I still can not log in to my admin/dashboard.

What’s strange is that I have three different sites. On two of the three there was no problem with 6.5. With this one … nothing but problems.

Are there any other ideas about how I can get logged in? I can use Ecto and make posts (which requires the same login and password that WP dashboard does). So this is very strange to me.

I also tried this. But this person instructs to “upgrade using Auto Upgrade plugin” … how does one do this when it’s not possible to get into the admin area?

Would I do well to upgrade to the new WP 2.7 release candidate and hope that resolves this? Any other suggestions?