On a system which ran 11.4M1 without problems I upgraded with zypper up to M2. I got some peculiar results (not all represented in the subject of this post).
Installation itself went flawlessly, but not so first boot. Grub presented the boot menu fine, but after choosing the regular M2 I got nothing but a black screen, and a lot of processor activity, to judge from the increasing fan speed. So I rebooted and chose the fail safe version, which booted all right and presented the kdm login screen. But a few seconds after giving user name and password, the login screen is presented again.
Rebooting again, I tried the regular version again, and this time it booted OK. Which it has done ever since, so I cannot reproduce the initial failure. But the kdm login problem is persistent.
From the messages I find, two seem irregular to me:
kdm: X server for display :0 terminated unexpectedly
which seems rather obvious in this case, and
startpar: forward read: Input/output error
of which I don't know if it has anything to do with the X-problem
By the way, the system on which this is running has also a disk set containing 11.3 final, which runs without problems, so I would not think of hardware failure.
I did not find this bug in bugzilla (M2 is even no possibility there...)
I have submitted bug 643362 for it.