Ok. I had exactly the same problem as cash_queen. There was one site and all pages in its domain that I could not get to see, but will load up all other sites. And it is now solved. I think izzmasterg's message above was of gr8 help, although I didn't exactly follow his advice. I did something different and it worked because I realized what I did wrong. Let me explain.
First just the solution for the impatient:
I re-did a setup of my router (mine is linksys, so I simply goto http://192.168.1.1 from my browser to access the router's setup options) from a computer that was connected to the router via ethernet. I did not change any of the options, but simply clicked "submit" and then "continue". Then I restarted that and my other computer that connects via wireless. THAT IS IT. I am now able to access that site that was eluding me and all in its domain.
But what happened, you ask. Here is my take:
I have a linksys wireless router and two computers - one connected by ethernet and another by wireless. Now, when setting up the comps (I had just moved), I reset my wireless router (manually) and then did the router's setup using my computer that was connected via wireless (btw, for the fellow who said he doesn't have any software with his router, you don't need a software. Just the url for your router which is usually generic to the model - so all linksys routers use http://192.168.1.1). At any rate, that was a big no no. You are supposed to use an ethernet-connected comp to do setup, not a wirelessly connected comp. I think maybe this did it. Or maybe not.
Izzmasterg, you seem to know what you are talking about. Could you chime in? Do you think my theory about what went wrong holds water? I mean, I and my wife have many times simultaneously visited the same site using same router, but never have this happen. Could it be that setting up router using a wireless connection makes the router somehow vulnerable for a "band line" problem during simultaneous visits? I agree that for a specific site to be blocked like this, you do need something specific to that site such as simultaneous visits. But perhaps it also needs some other problem (e.g., setting up router via wiireless) to actually become a problem?
Just curious. Cash_queen, send some of that cash my way, if any of this works for you. I can understand how annoying it can be. Sheez.
Mlaks