I have been having problems, too. Mostly, it is caused by my old but paid for Windows 98 machine. Now, I usually have Active-X controls disabled on my computer. That is how the malware folks foist bad things onto your computer - use of Microsoft's Active-X controls. I now crash my operating system if Roadfood tries to load an ad on my machine that requires Active-X to work. I go to System Monitor in the System Tools section of the operating system, and see Kernal Processor Usage is 100 percent. Reboot time.
A lot of those banner ads are Adobe Flash ads. They need a Cray supercomputer to properly run on. Now, I am not sure if those ads take forever to run on my machine, or if they put a time delay in there to lock up your screen so that you have to look at the animation of the entire ad. Of course, you are not going to get a straight answer out of google-sin-dication (googlesyndication) or doubleclit (doubleclick). If I get some time, I will look at some of the computer hacker message boards.