Airport connection problem

hi,
I have an airport express, not the newest, the one you directly plug into the wall.
It was working fine, but since we have a new router from our internet operator, someting won't work.
My router is a Motorola / SVG1501E (DOCSIS)
When i run the airport utility, i configure the AE but when i'm done and the system restarts the computer is unable to read the settings from the AE (error 10057) but the light on it is green (so good setted up i think)
Also when i select the speaker in itunes airplay, it gives a dialog 'connecting', after a while the box disappear, but it isn 't connected! No error message or someting
I turned off the firewall of my computer, but i don't know about the firewall in the router.
The router is from my operator, and i can't get to the settings (i think they disabled it)
my computer is a windows 7, i can try to run the configuration on my dad's pc (windows 7) or on my mac, but my mac is in repair

Is the problem my computer, the router, or the router firewall? I don't know what to do.

Thanks in advance and sorry for bad english

To get to the admin page of a Linskys open your browser, delete the home page address and the Linskys manual will advise how to get to the URL. From memory 162.198.1.1 and user name and password box comes up. Enter admin in each and that should take you to the basic set up page.

From there you should be able to rest everything.