Upgrade causing slow browsing, fine internet speed

Hi,
Recently I upgraded from Windows Vista home basic 32 bit to Windows 7 professional 32 bit.

Now however, my browsing speed is very slow and often doesnt work. It seems to especially have trouble with google related stuff (eg Gmail and google maps etc).
However when I finally get a page up, download speed for files are completely normal. Im currently using firefox 4, but I have already tried Chrome and Internet Explorer with no difference between the 3. Ive tried disabling/uninstalling firefox addons, Ive also tried with and with out an active firewall, and turning off my anti virus software. Ive also scanned my computer with my anti virus (Sophos) as well as Spybot Search and Destroy. None of this has helped either.

All other computers in my house hold are all browsing the net fine, including my laptop also using windows 7.

I have really run out of ideas, as my computer was browsing the net fine before upgrading.

Sorry if I have posted this in the wrong place or this has been resolved elsewhere, I am a neewbie to forums, and I couldnt see a similar thread.

Cheers

Are you using the latest network drivers? Also, things like java and flash player and any other plugins you use need to be installed with a new install.

Try changing DNS servers to opendns or google.

Yes, I have updated/ checked for updates for drivers. I have also re-installed most programs, I definately know I have installed java and flash player.

Thanks, Ill have a go at changing DNS servers, not that I know what im doing. Ill read up and have a go.
Cheers

Ok, so Ive had a go at changing DNS, I tried using googles DNS, that didnt help. I went to the website for opendns, I dont really understand what was going on, do I have to subscribe or get the free one? which contains ads?
anyways I then logged into my own router and changed my computer to match it.

This has resolved my issue. Thank you so much for you help, its been bugging me out for days!

opendns ip addresses are:

208.67.222.222
208.67.220.220

Just input these numbers in the preferred dns server and alternate dns server fields respectively.

i did try those numbers, randomly enough as they were on a tutorial somewhere on this site, however they didnt work either. But not to worry as I said, Ive got it working now anyways!

ok, so typing in the DNS made it work for about 30 mins, and hasnt worked since. Since then I have tried Open DNS (including subscribing and also downloading their DNS updater). So once again Im out of ideas....

Yer I havent had the internet working properly since the upgrade.
It was upgraded by downloading the iso file from microsoft. I needed to do a fresh install though, as my vista was only home basic.