I reinstalled the program, tried repairing, and then when the situation reoccurred, I hit ESCAPE a few times (don't remember why, unless out of sheer frustration), but on the fifth ESCAPE, the game continued without a hitch. Huh!
It's a rare DLC conflict. It can happen if you have The Exiled Prince, Legacy, and patch 1.04 installed. Note that there is another area later in the game where hitting escape won't work, so you'll need a permanent fix.
There's a lengthy discussion and solution in the following thread: http://answers.ea.com/t5/Dragon-Age-2/Freezing-issue-in-The-Exiled-Prince/td-p/219604
The solution further in worked for me: http://answers.ea.com/t5/Dragon-Age-2/Freezing-issue-in-The-Exiled-Prince/m-p/1413440#M1862
