Not sure what system you're using but you can try the following from that grub console that your system keeps booting into:
The above is just a guess the "hd" and the number may change depending on how you partitioned your system so you might have to make some changes.
From there do the following:
After that run:
The last thing you're going to do is this:
From there, it should reboot and boot back into the system. If not, let me know but that should do it. It has happened to me a few times and this is how I fixed it on my system. I'm currently using CentOS 6.4