[nffc]

I find that hard to believe, but anyway, we'll assume you do have it right.

Can you do this:
- Open a command line by going start > run then CMD
- at the command line enter "ipconfig /all" (without quotes) then hit enter.
- still at the command line - locate the entry "Default Gateway" and then enter "ping <address of default gateway>" and hit enter.
- Then enter "tracert bbc.co.uk" and hit enter again
- Right click a black area of the command line then Select All, then right click again and Copy. Paste it all into a new post.

Otherwise, have you tried turning it all off (modem, router, and any PCs) then turning it all back on starting with the modem, then 30 seconds later the router, then 30 seconds later the PC.

If you're still getting IP weirdness then hopefully ipconfig will reveal why