Are you one who owns a Google Android T-Mobile G1 and accidentally updated to RC30 and finding yourself stuck with a non-root G1, if so don’t despair because an ingenious forum member over at xda developers has found a way to get you unstuck.
xda developers member chavonbravo has found a way to revert your G1 back to RC29 and with ease simply by gaining the uploaded image then renaming it, copying to your microSD and then run through standard procedures for re-flashing.
The revert RC29 back to RC29 hack for the T-Mobile G1 does indeed work, so G1ers get to it.
Source — xda-developers