RHEL 6.3 vs RHEL 6.4 - X startup failed, falling back to text mode

I'm booting up my server to install 6.4 and after the prompt about testing the media, I get the following message flashed at the bottom of the screen:

X startup failed, falling back to text mode

And then it continues in text mode.

But when I boot up with 6.3, I don't get this message and the install continues normally in graphical mode.

Any ideas why this would be happening with 6.4?

Thanks!