Ok, today I received another WRT54GL (yah, too much money 😛 ) and updated it to dd-wrt v23-SP1 instantly and is now (once again) powering my wireless network.
Yay! and thanks to Cisco/Linksys for that fine piece of hardware and to NewMedia-NET GmbH for providing such a great image for this hardware 🙂
Ah, nearly forgot that: remember, never put the same IP twice in the static DHCP lease table, or dnsmasq is refusing to start (thus no DHCP/DNS)!
I managed to recover my bricked WRT54GL (I set the cpu clock frequency to an invalid value) by building a JTAG cable for a couple of bucks.