Video pauses when switching between application

I had opensuse 11.4 32-bits kde with nvidia driver installed from nvidia repo and at it i was able to switch between applications while playing a video file (such as wmv, flv, mpg…) and i could do another tasks that the video kept playing. It was very useful when i wanted to listen to the audio of some videos while doing something else on my pc.
However now that i have opensuse 12.1 64-bits kde with nvidia driver compiled “the hard way” it’s not possible anymore. Everytime i’m playing a video file as the formats mentioned above if i switch to another application the video pauses immediatly and i’m only able to make it run again moving the progress bar on the video player or closing it and opening again. (Clicking on play and pause buttons doesn’t have effect.) The same thing happens in smplayer and in kaffeine wich have very different engines so the problem doesn’t seem to be of only one application or engine.
sometimes this problem becomes so picky that once the video in smplayer paused even because I opened the preferences window of that own application.
Can you help me please?