I have an aggravating issue with my N4100PRO. It seems I can't access the web admin tool via either IE8 or FireFox 3.5 on my Vista PC with any sort of regularity. I get the typical "unable to connect" message, and the only way I've gotten it to work is to use the setup applicatin and login there first.
It's not a network segment issue, because I do get in after several tries. I can ping it fine as well - it just seems to be a problem with the admin application.
I've found nothing anywhere in this forum that addresses this issue, so if anyone has any suggestions I'd appreciate it.
i too had the same problem after purchasing and setting up the n4100pro. it worked for me by logging in the router to find the ip-address. mine is 10.0.0.1
i filled this ip address in the field of the gateway ip. furthermore the nas also needs a ip-address in this range. i chose 10.0.0.3 and assigned this ip address to the nas inside the router to prevent conflicts over the network with other devices. the following link leads you to a screenshot of my settings: