When installing 11.2 via KDE live cd, I chose a password that resulted in a warning to that effect that it was too predictable. However, I chose to “continue” with the install without changing it. My assumption was that it kept the password I chose. However, after the install completed, I was unable to login.
Do I have to re-install from scratch? Installation takes a few hours as this test machine is an old Pentium II with 256 MB or RAM.
Ouch that is barely enough memory. If your video takes up some (ie on board) then you may be suffering from a low memory condition. I would not even consider running in less then 512meg.
Try login from the command line (CL)
at the boot screen type a 3 to start in text mode
try logging in as user and root.
if you took the defaults in the install your user and root password is the same.
Also remember that Linux is case sensitive. So you might want to try the reverse case of the password. Your cap locks may have been on. 
You should be able to reset the password but a lot of the old methods have been locked down and I’m not sure what works now. Maybe someone else can elaborate.
Did you read the system requirements? This is by way not enough machine to get a proper openSUSE experience. Try some lightweight Live-CD first.