Just to say that it was a bug present in RH EL 6.0 and 6.1 + updates.
Workaround was to put
rd_NO_PLYMOUTH
parameter in grub.conf kernel line
This is now solved at least in 6.2 install media.
the problem arose at least in Qemu/KVM and Vmware virtual guests.
Probably a few guys put in forced single user mode with Linux... based on no answers until now ;-)
BTW: related bug should be this one