I have also been plagued with this recently and can confirm it is specific to an ad on this site (affecting me on IE and Firefox). I do not believe it is not the result of my machine(s) being infected with spyware.
My solution was to download the flashblock add-on which has solved the problem. One of the flash ads is hijacking my browsers. It appears to happen when the add area at the top or bottom displays a blank white banner. Then the next click hijacks everything.
Not sure how to best get this resolved but thought I would pass this along.
(hide) Keep your Inbox clean by Archiving important messages and regularly using the Delete All Messages in your Inbox option. (pauloaguia) (show all tips)