Please Help: Problem w/Browser Window-Keyboard Interface

I've noticed for some weeks that when I select text within either the browser window (e.g., to replace part of a URL) or even a text window within a website (e.g., a search window within Craigslist), and then try to replace that text by typing over it, I get no response. Nor can I delete the text I've selected. I have to backspace to delete the text. The selection does show up; the blue highlighting is there. It's just that the computer doesn't respond after that.

It doesn't happen within Word or other programs.

Computer is a Dell Vostro, bought new this March. Windows XP Home edition.

Unlikely to be a virus; I'm running AVG and updating it, along with Spybot. Windows firewall is on. I do the Dell PC Tuneup pretty regularly and defragged recently.

I haven't spilled anything on the computer or jarred it in a major way.

I've tried changing the ethernet cable, restarting--all the dummy fixes. I even tried it in a different city--no change. Using cable Internet both places.

What's also weird is that after a few minutes, the problem goes away, and I can replace text again.

Anyone have a guess as to what the problem could be? I could just tolerate it, but it's a new machine, and this is kind of annoying.

Thanks for any thoughts!

 

does this happen to/with all browsers that you tried so far?

cheers ...

 

First, thanks for the reply! I was afraid I'd be ignored forever for a bit there.

If by browsers you mean other Internet programs, I haven't tried any. I haven't downloaded Firefox or Mozilla.

If you mean text windows, then yes, it does this in all of them--like if I tried to replace selected text in this very window I'm typing in now--not just browser windows. So it seems obvious it's not something to do with my Internet connection. Something is causing a delay in whatever the program is that causes the screen display to recognize and obey keyboard commands.