You should see both the old Linux penguin icon that rEFIt showed you and a new Ubuntu icon.

REFInd, unlike rEFIt, enables you to boot Linux kernels directly. Your computer seems to have a BIOS-mode GRUB, which would require a hybrid MBR to work correctly.

It looks like you no longer have a hybrid MBR, which would explain why rEFIt has stopped booting Linux. That will give us some solid diagnostic information to help us figure out what's going wrong. Post that file to a pastebin site and post the URL to your document here. (It's available in the boot-info-script package in Ubuntu.) This will generate a file called RESULTS.txt. In any event, if you want a more thorough diagnosis, I recommend booting a Linux live session and running the Boot Info Script. OTOH, that could be a gptsync bug or some minor issue that's not worth worrying about. That said, you've got at least one other symptom that disturbs me a bit: the gptsync issue, which might denote a serious partition table problem. rEFInd may help because it can detect and launch Linux kernels directly, whereas rEFIt relies on an EFI or BIOS-mode boot loader - and based on the error message, it sounds like it's trying to launch Linux in BIOS mode but is running into problems with the boot loader. (Note: I'm rEFInd's maintainer.) If you want to play it safe, you can try rEFInd risk-free by using its USB flash drive or CD-R version (both available from the downloads page). One shot-in-the-dark solution is to replace rEFIt, which has been abandoned for over five years, with its maintained fork, rEFInd.

Mac no bootable device fix