Upgrade "not a root partition"

[Werner Kliewer <VKliewer mpi mb ca>]

Hi,
 
When I try to upgrade my installation of RedHat Linux 5.1 to 5.2, 
everything works fine until it asks for the current root partition. I 
tell it which one to use, and the install process says (something 
like):
    This does not appear to be a root partition
and refuses to proceed. What is the upgrade process looking for? What 
might I have done to this partition? It boots fine with lilo. In fact 
it is my default boot partition, even thought it is hda5, the first 
logical partition in the extended partition.
 
Werner Kliewer
Manitoba Public Insurance