Okay, for those who are interested, I found a solution and some (but not all) answers.
In brief: don't use chkconfig with SuSE, use YAST's runlevel editor instead. There are some runlevels in SuSE which chkconfig doesn't display. If you do
use chkconfig, run SuSEConfig after it -- I didn't do this, what probably caused the erratic behaviour concerning the boot messages ant the beginning. Oh, and SuSE says you have to run SuSEConfig...
Long explanation: After the excitement died down, I found what goes on on boot time
. There is also a SuSE README in /etc/init.d/README on this topic.
After the Kernel has done its thing it hands control to "init". /sbin/init controls the next steps of the boot process, first by evaluating /etc/inittab which tells it what runlevel to use.
Most important, though, it calls /etc/init.d/boot.d in which the runlevel is finally evaluated (the number is used to determine the runlevel-specific directory which hosts links to the start scripts which are started in a loop from here). And before that is a loop which controls runlevel "b", like boot, (SuSE-specific?) and kicks off boot.lvm, my nemesis.
Btw. /etc/init.d/boot.d also reads /etc/rc.status (which sets the pretty colors for SuSE's boot-screen) and /etc/sysconfig.boot (where the behaviour of the boot process can be customized).
Okay, so I used YAST to power down boot.lvm and got rid of the error.
BUT -- I never found out what activated boot.lvm in the first place, or, if it was active all the time, what caused the error.
Note for those who want to accelerate their boot sequence: chkconfig can delete or insert links to services for boot-levels 1 through 5. It does not
deinstall the module / service -- but YAST can...