In several GNU/Linux distributions as of late Skype interrupts audio/video playback in GNOME. One of those ditros happens to be Squeeze.
Once an application is playing video or audio e.g. Totem, whenever Skype plays a sound the playback is paused. When Skype finishes playing its sound the playback resumes or it does not.
From several versions to come PulseAudio can pause playback in media players by sending pause signal to them. This happens when a "call" tagged sound is played through it. One example of such "call" sound is any sound of Skype. Obviously the notification sounds should not be tagged as "call" but they are. Whether this is Skype's or PulseAudio's fault is out of the scope of this post. So when Skype plays a sound, PulseAudio sends a pause event to the current playing player and it gets paused.
In order to stop this behaviour we can disable the plugin of PulseAudio which is responsible for pausing/unpausing on a "call" sound. To achieve that follow these steps: