Belkin N1 Router/Modem problem - anyone have any ideas?

[#1]

Hey everyone,
     My internet and everything is fine now. However a week ago I returned an item on RMA, which was a nice new shiney router. Planned on giving my old one to my girlfriend as she will be studying in February with the OU
Anyhow, I originally sent back the router as it seemed faulty. I could get on the router page and put in the Plusnet username and password, but then no connection. Then I tried accessing the router page and get page cannot be displayed. So then I try resetting the router and get back on the router page, then i try and click on a different page within the router page and guess what, "page cannot be displayed".
Now I have been sent a brand new one due to this, and my 2nd attempt is exactly the same. The strange thing is I can plug my current Belkin router in and bingo, it connects fine as always. But this Belkin N1 just keeps disconnecting.
Sometimes I can't even get on the router page, and when I do I can sometimes enter user details after a reset but 90% of the time I just get, "page cannot be displayed" as soon as I click a link" or I just can't get on the router page full stop.
I think since getting this replaced router I have got about 3 seconds internet access at most, and no joke on that.
I am using Windows Vista. But don't believe this is necessarily the issue as I have tried using a standalone laptop and get the same issue.
I really don't know what to do now, surely I can't have 2 faulty in a row. Anyone ever had an issue like this or have any ideas?.

[#2]

Purely a suggestion:
Access to the router usually requires a user/password. The browser optionally caches this so it wont ask again for that visit. Perhaps the browser you use is not caching the passwords, or  Vista has some default security set-up like that?
I assume, of course, you are not trying to access it using wireless at this point?
I have heard of other people having problems getting Vista to work with a router, but other people strongly attack such claims as baseless. You kind of imply you did try an alternative OS.(?)

[#3]

Thanks for your reply, it all helps.
I tried a laptop, locally via LAN, excluding the ADSL Link to just see If I could communicate with the router. The OS on the laptop was Windows XP.
I can get on the internet fine at the moment with my current Belkin router which I have had for 2 years. The setup of the new router is pretty much the same, the standard username/password affair.
Its just so confusing that I could have 2 routers faulty.The password on the new Belkin N1 default password is blank(as i no password) which I have left alone.
Just tried a reset and managed to get on the router page again, but then went to a settings page and it just kept trying to load something and then page cannot be displayed. After that it just wouldnt show anything, very upsetting.
Not tried wireless yet but it would be handy so I could see if the PC was the problem, but I have crossed that possibility out due to the fact that I have tried a laptop to.
I think I could also exclude the cache idea, because I cant ping the router at the point that it decides to not work.

[#4]

Here an idea. I'm wondering, would it be a good idea to plug the router that works in and plug in the new belkin n1, and assign the belkin n1 an IP and try connecting to it through the network?

[#5]

Hmm...   Getting thin on ideas here, I'm afraid.
When I last changed router (but this included manufacturer too, so may not apply), the IP address of it was different, including the subnet. If you've set up any static addresses, gateways or netmasks for the connection they may have to change. Or maybe it clashes with some other piece of kit on a different interface, or even that the router itself is picking up wirelessly?
What about the firewall? They're favourite for suddenly making something un-pingable.
I asked about wireless to make sure you weren't using it, not to suggest you do! 

It seems very odd that the XP laptop, wired to the router, with nothing else connected to either, cannot reliably access the router's internal setup pages. I'd not worry about outside web addresses, or even other LAN addresses, until you can solve that bit. 

[#6]

Hey. I've just managed to get it working. How the hell I have fixed it I don't know though.
My strange solution is as follows:
step 1 - I used the provided wizard cd to try and setup the router. First attempt I got to the router is restarting and the router bombed out,
step 2 - 2nd attempt with cd wizard I got all the way through to connecting to the internet and it wouldn't accept the information, I then realised the router died again because I couldnt access the router page
step 3 - I then manually restarted the router and accessed the interface page, put in the settings and bingo it worked.
step 4 - left it connected whilst I got a cuppa. Then come back and i'm now browsing the plusnet forum, so it looks like its worked.
So it seemed like a mix of using the cd wizard and manually entering details on the router page fixed the problem. I did notice though that at step 3 the router settings I put in via the cd wizard didn't appear so it didn't seem like they where actually uploaded (even though it said uploading settings).
On another note, the first belkin N1 that was shipped to me did work for 3 days, it was only until I plugged my old Belkin router back in to change some settings before hand over to my girlfriend that the Belkin N1 stopped working.
So now I wonder, after a week of problems,getting the router replaced and going through this annoyance I got it to work. So what exactly could this have possibly been caused by?.