I'll go over again what I personally did..
First thing I did was make a NAND backup of my CM6 setup..I use clockwork recovery and always will..I've never had problems and don't believe anyone who says it doesn't wipe correctly.
Once I made my NAND backup I wiped data and cache...Then I loaded stock rooted 2.2 ROM found here
http://forum.xda-developers.com/showthread.php?t=743352
Rebooted and let the ROM load up for the first time..I didn't setup ANYTHING!!
launched dialer and enter
##786# - MSL - Menu-Reset
It rebooted my phone for me and I just let it reboot.
Once it rebooted it did the update crap.
checked my phone info and it took it the second time I tried
jump into recovery and loaded some old rooted ROM from like months ago and it also showed 1.40
NAND restored my CM6 install.