Topcom WBR611 unable to reset

Hi,

I'm using a WBR611 access point as a single router in my home network. One
central pc having access to internet is connected with a cable (rj45) and
the other ones are using wireless connections to the router.

I made a mistake by allowing only the MAC adresses of the wireless network
cards of the other c but I miss to enter the mac adress of the central pc.
So just after the "apply" the router was no longer accessible for
administration purpose.

I tried to reset the router in order to return to the initial factory
settings but it seems this is no longer possible.

Should anybody already experienced something like that?

Thanks for your help

Christian