Browsers automatically go back; new windows lose focus

Symptoms:

1. After a few seconds, browsers will return to the previously viewed page.

Happens with IE, Firefox, and AOL's version of IE.

2. Outside of browsers, after opening a new window, focus will return to the

previous window within one or two seconds. For example, clicking Start and

then Control Panel, the Start button's menu will move to the front. Control

Panel will still be open.

I suspected problems with the mouse or keyboard, so I reverted the mouse

driver to a generic one no difference (it's a Microsoft Optical). Unplugged

the keyboard in case a physical key was stuck (backspace?) no change.

XP Home, with McAfee, Spybot S&D, Spysweeper, AdAware, HiJack This.