It's an old issue, but it came up again in the forum today. For future reference I post it here, too. Per default SwyxIt! enables application sharing so that you can share your desktop or an application with another SwyxIt! user with a few mouse clicks. SwyxIt! uses Microsoft Netmeeting for this feature. When Netmeeting starts the whole screen flickers or, depending on the speed of your graphic hardware goes black for a short time.

If you're not using application sharing, disable it by unchecking the Enable Application Sharing checkbox in the user properties:

If you're a software developer you probably stumbled about another SwyxIt! default feature. You're debugging a program and try to step into a function by pressing F11, which is the default shortcut, e.g. in Visual Studio. But SwyxIt pops up instead and tries to dial whatever text has been selected. You can switch that off, too. Go to the Keyboard property page, select Dial selected number/URI and click Remove.