very slow keyboard response in IE (sometimes)

[Special K]

Occasionally I will be typing a new address into IE and it will suddenly start responding very slowly - I will press a key and it won't appear on the screen for almost a full second later. I can type in the whole address quickly, but it will just display it very slowly on screen one letter at a time. Once I hit enter, (or should I say once the keyboard/IE detects that I have pressed enter) it goes to the page and everything is fine again. I have noticed this on several different computers and I don't know what I am doing to cause this. It is fairly uncommon but I'd like to know what is going on. Has anyone else had this happen before or know what causes it?