Many things could cause this, but I would check the following:

1 - Do you have Norton Internet Security? Try disabling it. Clear your internet cache, and reload the FoD pages.

2 - Do you have the latest version of Java installed? The last PC I saw with Java problems had two versions installed which were conflicting. I removed both in Add/Remove programs then reinstalled from 

http://www.java.com.

 If you uninstall a version, try again before reinstalling - some versions of Windows have Java already. If you don't have broadband, it's a large download so don't try this, you might want to order a CD (or have someone else download it to CD).

These are just two ideas, and neither might be the solution to your problem. If you are unsure about what I have said, please find someone who understands rather than risk causing problems with your computer. Good luck!