I cannot investigate this further, as I'm doing renovation of my
computer room here and I'm not having the soekris connected to com1.

What I see is: If I turn on the dsl modem AND the soekris4501 at the
same time (this would always be the case after a power failure), mono
starts up, but the Error LED on the soekris stays red.

It seems as if it is because the dsl modem is not yet connected. I
don't know which process in m0n0wall does fail, but, shouldn't it
retry?

Maybe someone else has seen this problem.

I've got the latest m0n0 1.2.1.