I use MS IE and use AVG Internet Security 2011 and haven't had any problems with is board or any other place I go online.
You may need to update whatever web browser you use and also check to see if there are updates for your virus scanner assuming you are running one on your computer.
Also never open or click on any "warnings" link. Do not click on X type pages or symbols. Instead go to your task manager and close it. If you don't you take the chance of a virus taking over your computer.