I recently bought a Dell Inspiron and installed Ubuntu Jaunty Jackalope on it. I was having a hard time making skype work on this. Every time I started skype, it gave me a "Problem with audio playback" error. I googled a lot and on Ubuntu forums found following solution to this.
First go to Skype->Options->Sound Devices and set "Sound In", "Sound Out" and "Ringing" all to pulse. Uncheck the "Allow Skype to automatically adjust my mixer levels".
Now go to the volume settings by double by clicking on the speaker icon on top panel. Here in the preferences, check the capture option. Now in the recording tab unmute the mic.
Go to Skype and make a test call. Everything should be working by now.
This solution was found here.