For some users, external displays are exhibiting a series of all-too-familiar issues under Mac OS X 10.6.3. In the most common case, external monitors no longer function at the desired (usually highest) resolution. The external display remains blank until the resolution is switched to a lower setting from the Display panel of System Preferences.
In other cases, the external display will not function at any resolution, or the display flickers or exhibits other distortion.
The problem appears to be most prevalent with Samsung monitors.
Possible fixes
- Lower the resolution. As aforementioned, this issue generally afflicts higher resolutions. As such, you can work around it by opening System Preferences from Apple menu (upper-left corner of the screen) then choosing Displays. Select your external monitor and reduce the resolution. This doesn’t solve the issue, but may restore the display or eliminate flickering.
- Downgrade to Mac OS X 10.6.2. Users who have downgraded to Mac OS X 10.6.2 have reported elimination of this issue–a less-than-ideal, but in some cases necessary workaround. See this article for downgrade instructions.