I honestly give up for now.. trying to install via update.zip gives me a verification failed or identification failed error and doesn't even start.
Trying to do it OTA goes about 1/3 of the way stops, reboots, and then says it failed.
Would love to know what the problem is because my backup was made literally the day after I rooted and I have never removed or frozen an application.
Mine is now working on 2.3.340, andylulzyou.
I was grasping at straws. I hadn't removed any apps when I was rooted, or done much of anything beyond installing Setcpu and wi-fi tethering.
Somewhere along the line, I modified my build.prop file, though.
When I restored my build.prop file from the backup of the original stock file, my update went through perfectly.
Something to try if you ever modified your build.prop.