preupgrade not Upgrading F14 to F15

[Varuna Seneviratna]

I used preupgrade to Upgrade F14 to F15.Finally preupgrade issued a
message to reboot for the upgrade to take place.I have Ubuntu and
Fedora both on my machine.By mistake during the reboot the machine
went into Ubuntu since it was the default selection on the OS section
menu of the Boot loader.I by pressing the restart Button restarted the
machine and Got Fedora Booted Up But the Upgrade from Fedora 14 to
Fedora 15 has not taken place.When preupgrade is started it is agian
starting from the begining.

Why is this?
What can be done during the next phase of upgrade to start from the
point it was left off?