The fact your modem has a different ip address from you, leads me to beleive it is a router also. Why it did not display a page i do not know for a fact, but suspect your using the wrong ip.
Here is a simple method to test if u have a router, almost never fails, in mirc while connected type in....
/localinfo -h
<wait 5 seconds>
//echo my lan ip is $ip
<wait 5 seconds>
/localinfo -u
<wait 5 seconds>
//echo my internet ip is $ip
Now if the LAN one of them comes out looking like something like 10.0.0.2 or 192.168.0.100 really anything in the range 10.0.0.??? and 192.168.???.??? means u have a router.
Now your routers Ip might not be what you expect it to be, so heres one way to get it, in mirc type /RUN CMD this opens a dos box, in that black box, type IPCONFIG /all
Look for the adapter with the IP the same as u got above as your LAN one, then look near that for a GATEWAY ip, that well be the ip of your router.
If this doesnt all pan out, come back with the make and model of the modem.