I installed Ubuntu 11.10 alongside existing 10.10. I expected to get a menu on startup to choose which version to start with. It booted straight into 10.10 and I didn't get the option of 11.10 at all. How can I get the menu at startup?
Problem solved. It appears I inadvertently overwrote the MBR in sda when installing the other OS ubuntu 11.10 alongside the existing ubuntu 10.10. Warning if you are going to dual boot - when asked where to install bootloader put it in your ubuntu partition, NOT in the root of the hard disk otherwise you will overwrite the MBR.
Solution: Using "Try Ubuntu" from live CD or USB follow the instructions in this link
install the Boot Repair utility. Check Fix MBR and in the MBR tab repair it. Take a note of the instructions given in case the bootloader is trashed and restart.
When I did this grub produced a menu from which I could choose either Ubuntu 10.10 or Ubuntu 11.10
Hope this helps.
First, did the 'hold shift' answer from root45 work?