I'm on the latest upgrades and can't have strange problem's with Skype.
I've just setup a ThinkPad T420s with LMDE, so this never worked before...
When I try to play the testsound all I get is silence, but when skype trys to play a signal ton or so I end up with strang disturbing sounds!
The same happens with ekiga, while VLC is fine...
Found a solution by accident: