OK here it is! Thanks to everyone who might help with this issue!
PS: I am aware of the FAQ page you mentioned, but sadly this doesn't
impact my problem.
>> I have fiddled some more with my m0n0wall, unsuccessfully. Would anybody
>> know why the m0n0, when there are "pass-all" rules (ie. any proto, any
>> source/dest, any port allowed) on all interfaces, might still reject
>> some traffic? Maybe this is a known bug??
> Please post your (anonymized) config.xml, otherwise this will lead
> nowhere. Also, be aware of this:
> - Manuel