Installation of RHEL5 via kickstart fails with "You selected packages require 2789 MB of free space for installation, but you do have enough available. You can change you selections or reboot" error

Issue

Installation of RHEL5 via kickstart fails with "You selected packages require 2789 MB of free space for installation, but you do have enough available. You can change you selections or reboot" error.

74 % done ... error generated:

You selected packages require 2789 MB of free space for installation, but you do have enough available. You can change you selections or reboot

The partitioning section of kickstart file is as follows;

bootloader --location=mbr --append="rhgb quiet"
#clearpart --all --initlabel
#clearpart --all
clearpart --initlabel [disks]
part / --fstype ext3 --size=21373 --grow
part /boot --fstype ext3 --size=256
part /var --fstype ext3 --size=8192
part /opt --fstype ext3 --size=4096
part /usr --fstype ext3 --size=2631
part /home --fstype ext3 --size=1024
part /tmp --fstype ext3 --size=4096
part swap --size=4096