X or kernel or mingetty broken after update

Hi. 
I am using fedora 11.
Last weekend I performed a major update - 133 packages. Now I have a problem that renders
the computer usable only remotely. Something is wrong with consoles, X, or the kernel. Not
sure how to determine the culprit. Here are the symptoms:
Say I start with a fresh telinit 5.
1) If I get into an X session, CTRL-ALT-F2 (say) does NOT take me to a vt.
2) If in KDM, CTRL-ALT-F2 does take me to a console, but if I then try to go back via
ALT-F1, I get blank screen and no response to keyboard from this point on.
3) I think if left alone in runlevel 3, the keyboard/screen eventually locks up too, but
not too sure about this.
4) To get it working again, must do telinit 3 then telinit 5 from a remote login.
5) In system log I get:
    /sbin/mingetty[16865]: tty1: invalid character 0xbb in login name
   init: tty1 main process (16865) terminated with status 1
   init: tty1 main process ended, respawning
This happens many many times, every 5 sec or so, with different "invalid
characters"
6) ps ax lists several (about 10) kerneloops processes that don't seem to go away.
   18600 ?        S      0:08 /usr/sbin/kerneloops --nodaemon
   19155 ?        S      0:07 /usr/sbin/kerneloops --nodaemon
   20063 ?        S      0:07 /usr/sbin/kerneloops --nodaemon

How do I go about finding the problem and how can I revert to a working system?
Thanks!
Ian