It could be that GRUB wasn't installed in the correct hard disk or you might have a CMOS setting (BIOS) which prevents any programs writing to your first hard disk's MBR.
You should be able to try again to install GRUB 2 to MBR using your Ubuntu Karmic Koala 'Desktop' Live/Install CD.
Try booting with your Live CD and then mount your hard disk installed Ubuntu operating system.
Take a look in /media to see what the name of the mount point is or ls /media,
You should get a nice user-friendly name for the mount point if you set a file system label, otherwise you might get a file system UUID number which can be rather long and cumbersome.
You can set a file system label by right-clicking on your partition in GParted, for example I simply call mine KARMIC.
Regardless of whether you set a label for your file system or you're happy to stick with the UUID number, open a terminal and run the following command,
Where /media/KARMIC is the mount point for your Ubuntu file system, otherwise it could be some other name or a UUID number. Feel free to replace as appropriate.
sudo grub-setup -d /media/KARMIC/boot/grub /dev/sda
If it complains about not being able to open /boot/grub/device.map, you might need to hold it's hand and specify the path to the device.map file with the -m option, as follows,
If it still doesn't work try looking in your CMOS and disabling any MBR write-protect feature you may have left enabled, it may also be called something like 'boot sector antivirus' or some other name.
sudo grub-setup -d /media/KARMIC/boot/grub -m /media/KARMIC/boot/grub/device.map /dev/sda
If your computer has more than one disk you might need to change the '/dev/sda' part of the command to /dev/sdb or something else.