If someone figures it out post it in that thread so it can be added to the original post.
Who created the nandroid/sprecovery setup? I've asked this before: if the app spits out error 6 then someone coded it to do that in certain situations. Anyone know who that someone might be so we can update the above link with a more exhaustive list of error codes?
I tried looking through the nandroid.zip file with all the code and there are just too many files to look through, none had names that hinted towards error codes.
fyi, this exit with code 6 occured while trying to install an update.zip