I know there are already a lot of posts about this error message, and
therefore I'm almost sure it has to be the CMOS battery  that causes
ther problem.

However, since the boot stops completely after giving this message (not
even one line of text more)
it might just be something else.

The beep-code is also different: two short beeps, pause, one longer
beep, and then it starts rattling short beeps whitout stopping..

Can anyone tell me what the solution moght be?