SOLVED: cannot login after Cauldron updates

I know what I did, I think, but I have no idea how to fix it.
One of the last updates was something called setup and it prompted me to accept or reject two of the updated files. I accepted them. I figured that this would be safe enough as it was an option and there was no specific warning about what dire consequences acceptance might bring. Besides, I knew from Mandriva days how to boot to single user and fix any fundamental breakages, but I must be mis-remembering because it still wants me to enter a root password which it has changed from the one I set on installation.
So if anyone knows how to fix this I would be pleased to hear. If not it is no great problem as it is a test system in a VM and I can start again from scratch. However, I would like to know how to choose the correct action when faced with a choice of updating these setup files again...
R
One of the last updates was something called setup and it prompted me to accept or reject two of the updated files. I accepted them. I figured that this would be safe enough as it was an option and there was no specific warning about what dire consequences acceptance might bring. Besides, I knew from Mandriva days how to boot to single user and fix any fundamental breakages, but I must be mis-remembering because it still wants me to enter a root password which it has changed from the one I set on installation.
So if anyone knows how to fix this I would be pleased to hear. If not it is no great problem as it is a test system in a VM and I can start again from scratch. However, I would like to know how to choose the correct action when faced with a choice of updating these setup files again...
R