Text Changes don’t update on a few computers…

I have a PC running xp that is having trouble updating and posting new pages. I can do it from my computers and other computers in the office. But this one computer is not allowing me to update text and pictures on pages. I updated the computer and browsers. It started to work with IE8 but then stopped. With Firefox it did not work at all. I change to the default theme and it still does not update.
What can I do? Please any ideas would be helpful.