verified on 6.3-20120621.0.el6_3:
upgrade rhevh-6.2-20111117.0 build to 6.3-20120621.0.el6_3 via rhevm, tui and kernel cmd line are successfully, the default boot entry is 6.3.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
http://rhn.redhat.com/errata/RHBA-2012-0741.html