Strange that some Sties are loading and not others..can you see a pattern like Irish sites are loading and uk ones are not..or UK are not loading and US are not?
If some site are loading and others aren't It wont be a browser issue, provided you cleared all your cookies?
you can testing your routing to see if it's an ISP problem.
go to start, run , in the run box type command(or cmd) click ok
This should bring up a black box(dos prompt)
at the flashing cursor type>> tracert goolge.com (I'm using ggole as and example, use one that works)
Now what you see back may look like nonsense to you but whats its doing is showing you the the path or "route" you are taking to that site by various "hops". It should start at the address of your HUB ..something like 192.169.1.1 or 192.168.1.254..that doesn't really matter... that's your gateway, the first step, the next will be external IP address provided by your ISP.
So it will take another few hops and you will probably see your ISP's exchange router
like this
blah-blah.eircomarecnuts.path.hairyfanny [10.1.1.0) or some sh*t like that...
you don't need to interrupt any of this, just so you have a reference point. count the number of hops..usually around 12-20 depending on your isp.
So now run the same for a site not working, you could open up another command prompt so you have them side by side for comparison.
tracert scoobynet.com
now compare the 2, for the one not working you may see a drop off or it stopping at a certain hop. Now I wouldn't expect you to do anything with his information, no one can really expect your ISP....
but at least you will know it's a routing issue and when you call the useless cnuts at the help desk you already have proof that they have a routing issue and you will save yourself days of endless back and forth with someone who knows less than you reading from a script designed to get you off the phone and confused.