I think the animated ads have a LOT to do with it, because I've recently had a strange problem with a message that pops up in the middle of a puzzle..
It usually says something about a flash player 9 (adobe) that is causing my computer to run slowly. Now, I do know that this is an older computer, but it has occasionally wreaked havoc on my solve time, as I have had to close the window out and start again.
This has been a somewhat recent development. I really DO think the ads are the main problem. Once I accidently clicked on one and it was so bad that my computer "locked up" and I had to re-start it.
Maybe it's the fact that my computer is old, but I really think those silly ads are part or most of the problem.