You can tell when you are booted off of the installation CD(or any boot disk) by opening Disk Utility and selecting your drive name. At the bottom you will see your volume format. I highly doubt your volume is UFS because it is not the default. More likely it is HFS+ without Journaling and it could be that Leopard requires journaling to be turned on.
This requires erasing and reformatting so you should back up your data and then reformat as HFS+ Journaled.