I had the same problem. I ended up upgrading to 3.2.5 and then downgrading. I tried a lot of different ways to edit buildprop and nothing would stick after a reboot.
I put the steps I took here, http://forum.xda-developers.com/showpost.php?p=60186871&postcount=82.
I'll try that. I downloaded the 3.2.5 bin and put it in the sdcard folder. But when I go to System Updates, there is no Update button. Just 'Check Now' which wants to use WiFi.