Inspiron 6400 not displaying webpage?

I have a colleague from work that asked me to help her as for some reason her laptop was unable to view a webpage. She had a website but could not access the adminstrator login page. She could on other computers but not on her Dell Inspiron 6400. She had Vista so I immediately thought it must be a bug with Vista. She said another friend of hers tried it on their 6400 and it didn't work either. When I got home I tried access it on my 6400 and again I could not get the webpage to display. I however have XP Pro so I'm guessing its not a Vista problem.

The problem was the same across all the 6400's. The page will just appear blank, as if a blank page was sent to the browser. The address is in the title and there is no source. We have tried both Firefox and IE and got the same result.

Anyone ever had a similar problem? The real problem is she got a company to build her a website and set up an online shop with a back-end admin section for her. She spent a lot of money with them. I decided to try log on via FTP to the server and have a look at the php pages to see if I could hopefully locate some sort of problem. When I rang her website company they said that if they gave us the FTP username and password they would not be liable to any website problems such as crashing, losing info etc as we would have the password.

So....... Who is responsible? Is it Dell for having these problems with the 6400's? The website company for creating / using a shop program which cannot be displayed on some computers? Or is it hers?

All she wants is to get it sorted so she can update her site easily without hastle.

Any help would be greatly appreciated. Thanks