why wont my laptop let me access either yahoo mail, facebook, or google?

[stitch]

it hasnt let me read my messages for a while now on yahoo mail. today it has decided to put up cannot find server every time i try to access facebook. and with google, it says itis a forbidden domain.
why?
is it something to do with the bullguard antivirus i have? or does the computer just not like me?
any advice appreciated

it wont connect to bbc.co.uk or geekstogo either.
the only website it seems to be connecting to is mumsnet.
help!

Stitch, when you had this problem before I think you tried using this DNS server in Network connections.

4.2.2.1

Well if you still have that there it may be the problem now. I use that one and it started going wrong late last night.

I don't know if it's being fixed or what, but I changed to these for now (in that order) and mine is working again.

4.2.2.4
4.2.2.2

============================================
In Control Panel open Network Connections. You should see an icon in there for your internet connection. Right click that and select select Properties.

Now you should see a box with some lines of text and the bottom one says Internet Protocal (TCP/IP)

Double click that to open up another box which near the bottom says 'obtain DNS server automatically'

Tick 'use the following DNS server addresses' and it will let you type these two iP numbers into the boxes below.