Just tested the monitor on Mac OS X version 10.5.7 using a DVI cable with pin 16 removed. I can confirm that the workaround which was broken by 10.5.5 is now working again.
Just a recap: 1) Connect the monitor using a DVI cable from which pin 16 is removed (as described in earlier posts in this thread). 2) Use the "Enter" button on the monitor to switch to HDMI mode. The screen should turn blue. 3) "Detect displays" in Mac OS X. Now when you press "Gather Windows", the second window should be titled "BenQ G2400W". 4) Use the "Enter" button on the monitor to switch to DVI mode. 5) Enjoy!