My suggestion is to try the instructions here to temporarily disable IE add-ons and then see of the problem reproduces (scroll down to the item that says "How can I disable a browser add-on?"). If that fixes it, you can try the instructions there to permanently disable different add-ons until you find the one that is the issue.
Also, make sure you're running some antivirus and anti-spyware software. The free Microsoft Security Essentials program is pretty decent if you don't have any.
The IE 8 Javascript engine is pretty slow compared to other browsers, so if your computer is an older/slower one, it might just be that those web sites have some script that is running on key presses in a form field, and the system just isn't keeping up.
You were certainly on the right track ...
Before I posted here at FR, I came across an old Microsoft Forum where the MS Engineer recommended the same thing for someone - I tried it, but it didn't work.
Yesterday I left my own post at the MS Forum and just got a response from an MS Engineer suggesting that I try to disable each Add-On one at a time to see if I could nail the sucker ...
Lo and Behold, [and unbelievably], it worked on the first one!
It was Adobe Shockwave Flash Object. I disabled it, shut down IE8, then re-started IE8. No problem at the web site like before.
I then shut down the computer and re-booted. I opened up IE8 again, went to the web site – no problem!
I then enabled the Add-On, shut down IE8, then re-started IE8. Went to the web site – no problem!
I then shut down the computer and re-booted. I opened up IE8 again, went to the web site – no problem!
Thanks for the suggestion !!! Much obliged !!!