I have, for quite some time, a dual boot setup on my MacBook Pro with MacOS X (minimal setup for emergencies) and Ubuntu (the system I use daily). I have ReFIT 0.14 installed. I am running this setup on this machine for well over a year without an issue.
This morning I rebooted my MacBook and when it came back up, it showed the ReFIT menu but the Linux entry would not work. When selecting it, all I would see is the penguin, and nothing else happens. Booting MacOS X works fine.
I have access to the file system via fuse-ext2 on MacOS, and looking at the logs the laptop booted the last time on October 22nd. The only system update afterwards was this morning, but only for git, some xserver input module, ruby and macfanctld. No updates to grub or the kernel.
I am a bit at a loss what to do, any pointers are greatly appreciated. I already reset the NVRAM and the SMC. I also tried syncing the partitions but it refused to do so due to "analysis inconclusive" (the MBR partition table shows two additional partitions at the end (Linux root and swap) that the GPT table does not, however the GRUB partition is shown in both).