I just purchased a Dimension e520 2 months ago.  I have a Logitech cordless mouse and haven't had an issue up until 2 weeks ago.  I will open up the ie browser, click on the page and then use the scrolling wheel to advance down the page.  Right away the text size changes with each movement of the scrolling wheel and the text goes from my default setting of'medium' to 'larger' and 'largest'.  Then I will scroll the opposite way and it will reverse and up up at the 'smallest' level.  At the same time I am unable to click on any other open windows and my address bar and icons at the top of the browser are a mess.  Sometimes after a few minutes it somehow fixes itself and after clicking and righ-clicking I am able to get it back to normal.  But a little later it will repeat itself.  I have to close all of the windows and try again. I have Nortons antivirus and am clean.  I have run a complete scan several times after this occurs and the system is free of any issues.   Any help would be appreciated.