I just recently upgraded from RH5.0 to RH5.2.  When the
install decides to install lilo, i tell it where i want to
install and which partion is the default.  (these do not
affect behavior)  Then it goes and tries to install lilo and
it comes up giving an error message "Error: unable to
install boot loader"  Then it prompts to go back or to go
the menu.

Specifically whats going on behind the install gui, is the
lilo.conf file that is being written to /mnt/etc/lilo.conf,
is invalid.  I check out the file and was surprised to find
that not only did it include my main win95 partition as a
bootable partition but also, it included every one of my
fat32 + fat16 partitions as bootable.  These others are not
and no where else in the install did I say that they were
bootable.  These were all located at the end of the file
each under its own subsection other=....

To reproduce the bug, I suggest the following:  partion a
disk w/ 1 fat32 partiton, 1 extended partition, 1 linux
partiton and 1 linux swap.  I the ext partition, make 2
fat32 partitions and 1 fat16 partitino.  Install RH 5.0.  In
disk druid, give mount points for all dos partitions.  Make
sure the only bootable partitions are the primary fat32, and
the linux partition with the linux partions set as active.
When its time to install lilo, install it in the 1st sector
of the linux partition and make linux the default.  Boot and
make sure it works.
Next, boot the rh52 install disk and do an upgrade.  Dont
add/delete new packages simply update ones already
installed.  when lilo install comes up, pick same settings
as before, you now should see the error screen.  Hit alt-f2
and take a look at the /mnt/etc/lilo.conf file its trying to
write.

Workaround:  use the rescue disk to boot into single user
mode with the root partitino mounted.  manually edit
/etc/lilo.conf (just delete the extra stuff at the bottom)
run lilo and then reboot.