From this forum post:
Here are the steps i used to fix it.
Note that any mistake in recreating the partion will result in losing all data and/or the server will not reboot.
I would do this as the first step on a newly created instance.
I have marked the steps with <<#>> in the block below, so the are not a part of the command.
You need root permissions, so do a "sudo sh" if you are not root.