Maybe you have a pop up blocker enabled on the DIS site. Have you installed any new virus protection or anything else like that lately? I know that I couldn't get the "more" smilies or any pm messages to pop up in a new window until I added the DIS address to my "allowed pop ups from..." list.
Not only is there pop up blockers in new virus protection, but also in the mail, like yahoo, or aol, or verizon. I recently got verizon dsl and they had put pop up blockers automatically on my system for all sites without me even knowing it had happened until I went to use something here on the DIS.