Vista - Vanishing sliders in Vista volume mixer

Odd one this - googled it and didn't find much. I just noticed that when i open the volume mixer, it'll initially come up with some or all of the running apps using audio, but if i close it and then reopen again, one or more of them has vanished. This seems to be erratic rather than following any pattern. Any ideas? Like i said it's not something i've come across before. I reinstalled audio drivers, didn't help.

32bit Home Premium SP1 on Vaio VGN-N38E laptop.

applications take exclusive control of your audio even if theres no sound in there, you will get a slider for all programs that are open, its quite handy when you install a game with annoying music they insist on playing while installing, you can use the sliders to turn the volume down, if there are sliders disappearing, that usually means you have programs that are opening and closing in the background, spyware scans or something similar, i shouldnt worry too much about it.

well i wouldnt worry, however i turned msn right down earlier, and now the slider has gone and i can't turn it back up again!

ok, if its something like that, the messenger window wont show the application unless theres an audio stream coming from the application.
just to better explain, first pic is with MSN closed, as you can se, no slider for it,
second picture is with MSN open but no slider because theres no sound from it,
third picture is with the slider open on there because someone signed in, but if no one signs in, then you can create a sound wave, just go to the tools and select winks, this will bring up a slider called winks when you play a wink, close this and the winks window will switch to windows live

Yep, opened mixer, opened an msn window and threw a nudge, and msn slider came up straight away! Knew it'd be a simple answer, cheers for that MrNeeds!!

glad to be of service