AV update cannot connect to server


i have an issue with the AV-database update. It appears as though CIS doesn’t use a normal dns host to download the base.cav?

Here’s what happens on my machine: I have a wlan router that connects to my other, “real” router. The problem is that this one needs a PPPoE connection with username & password (and seems to have issues to assign a correct IP, so when using a cable prior to switching to wlan, I had to assign an IP manually). Yes, that’s 2 routers in a row, there’s pretty much nothing I can do about that.
So here’s my setup visualized:
DSL — ISP-Router — WLAN-Router ~~~~~ PC

I can push through the PPPoE password without any problems, so all my usual internet connections work perfectly fine. Windows also tells me it has complete, unlimited access to internet/DSL.
The CIS software update works fine also. However, when PPPoE is not active (‘disconnected’), any www address I enter takes me to the config of my WLAN router (which is fine).
As said before, once I connect via PPPoE, everything works fine EXCEPT for the AV update! (The msg I get is: ‘Unable to establish an internet connection’ or something alike)

That’s why I assume that AV update for some reason ends up on the config page of my router (which sould just not happen).

Any suggestions or ideas how to solve that?
E.g. what is the address/IP used to retrieve the update? Maybe an entry in the hosts file may help?


oops, I forgot: I’m currently running Win7 and my CIS is v 5.1.17588…
the wlan router is an avm fritzbox (the config address should usually be “fritz.box”)