First I want to add something, because I am using COS version 7.9.1 (Final) and not 7.2 like I mentioned earlier.
Your remark made me think and I realized that I didn't have the COS box as an additional DNS server on my Windows clients.
After adding that to it's IP4 settings, I was able to access the COS web configuration page with the correct aliases, so I think that solved the problem.

The only problem that remains is that even after adding an additional ip address to the Windows clients (192.168.178.# of the router), I am still unable to access the router page directly.
If I want to do that I have to connect my workstation directly to my router, after manually giving it an ip address in the same range (192.168.178.# of the router).
It would be nice if this could be solved too, but I don't know if this is a COS problem.

Please advice,

John