Dual booting 11.3&lucid lynx

I want to try OpenSUSE but don’t want to get rid of Ubuntu yet.
How can I install it so I will be able to dual boot?
I have an empty partition of ~150GB ready for it.

When I am installing OpenSUSE 11.3 I get this content in the boot section:

The bootloader is installed on a partition that does not lie entirely below 128 GB. The system might not boot.
• Boot Loader Type: GRUB
• Status Location: /dev/sda1 (extended)
• Change Location: 
• Boot from MBR is disabled (enable)
• Boot from "/" partition is disabled (enable)
• Sections:
+ openSUSE 11.3 (default)
+ Linux other
+ Failsafe -- openSUSE 11.3
• Order of Hard Disks: /dev/sda, /dev/sdb

sdb I believe is the USB key I am installing from and the Ubuntu partition is not recognized as bootable. How can I install it so I can still boot to Ubuntu?

You could install suse and see if it boots OK. Chances are it will.

Or install grub to the root partition only.
Then re-install grub 2
https://wiki.ubuntu.com/Grub2#Recover Grub 2 via LiveCD
When back in Ub* do: sudo update-grub
and all will be well in the world