Distorted video on Acer monitor using closed clamshell mode

I have a 15" Mid-Late 2007 MacBook Pro that I'm using in closed-lid mode with an Acer AL1917w monitor (DVI connection). After upgrading the Mac to Mavericks (10.9.2), I can't get the Acer monitor to display a non-distorted image when the Mac goes into closed-lid mode. With mirroring turned on and the MacBook Pro open, I can set the preferences to the highest resolution and I get a perfect image on both the MBP screen and on the Acer.

However, when I close the display lid and the machine goes into closed-lid mode, the Acer monitor image changes to a slightly stretched, distorted image. This happens no matter what resolution I choose from the Displays preferences resolution choices.

Again, it worked fine under Mac OS 10.5, but this problem shows up under 10.9.