Beware: This is at your own risk, because I have never done this myself (I just let the boot menu grow until it is time to freshly install a new Ubuntu release) and I may be wrong about some steps. Even though the chance of that is small, I don't guarantee any success so don't blame me if it goes wrong.
Start Ubuntu with the latest kernel version (prob the most upper in the boot menu). When you booted the OS, go to system --> management (I can be wrong about the name 'cause I run it in Dutch, but it should be similar to that) --> Synaptic Package Management.
When it is started, click on search (leave the field left next to it blank!) and enter the keyword "linux-headers". Of the older versions (check their version numbers) you should be able to uninstall them via a right-click on the check-box to choose for removal.
After applying the changes, you can close the program.
Go to Applications --> Utilities --> Terminal and enter the following:
##The code that makes sure that you will, using root priviliges, update the configuration files of your GRUB bootloader
Hit enter and enter your password (not dots or asterisks appear, but that is normal). After you have done so, hit enter.
Reboot your system.