Screensaver activates randomly after installing Lion
If you have a display extension or management application installed before upgrading Lion, you may experience problems with some display services after upgrading to Lion.
Do you want to install Lion on your Mac, but use a program that extends your display? Not so fast.
You might need to first update the programs or even uninstall them to avoid a screensaver-related bug they could cause in Lion.
As Apple adds new services, device support, and other features to OS X, the included programming libraries that developers use to write their code also change, which can lead to problems. In the case of display management and extension programs, while the programs still function as they should, changes in the frameworks they use can prevent the system from recognizing details such as when to dim, sleep, or activate the screensaver. As a result, if these programs are installed, the system may randomly dim the display or activate the screensaver.
Some of the common culprits for this behavior are AirDisplay, LaunchBar, and DisplayPad that have options for extending your Mac's screen to iPads; however, other programs may also show this problem if they support similar features.
While one solution to this problem is to disable the system's screensaver and display sleep options, this may not be a desired solution. Therefore, another approach is to update your version of these programs if you have them installed and if the developer has an update available. But if not, either uninstall the program or disable it to prevent the problem from occurring.