Are you working with Premiere Elements 11 Mac (purchased from Adobe), Adobe Premiere Elements 11 Editor (Mac Only) from the Mac App Store, or Premiere Elements 11 Quick Editor (Mac) from the Mac App Store?
Is this a "worked before but not now" or "it never worked before" issue?
Do you have the latest version of QuickTime installed on your computer with Premiere Elements 11? Have you checked your permissions?
ATR asks some great questions above. Would certainly like to know where you purchased your Premiere Elements from.