After rebuilding my initrd to test some kernel changes I was working on
my boot was hanging when gdm should start (using the charge plugin the full logo
was shown, then hang).
CTRL-ALT-DEL still works (and I guess ssh-ing in would also work I haven't tried).
Downgrading to plymouth-0.8.0-0.20100114.2.fc13.x86_64, fixes this (this was
the previous version my system had according to yum.log).
I've also tried with a vanilla F-13 kernel (before my kernel work gets blamed).
I would love to help debug this further, but I need to know what you need to know :) I can "bisect" this to a certain plymouth build, I can ssh-in and run strace, whatever you need ...
I've also searched for dups before filing. This seems like a dup of bug 546721, but that was with an older plymouth then the one which works for me. Bug 566846 *might* be related, same for bug 578196.
You need a newer gdm (2.29.92-6 or later)
*** This bug has been marked as a duplicate of bug 577789 ***