From Jeff at Google Analytics:
The demand for Google Analytics exceeded our expectations. As a result, we have temporarily removed the site overlay tool report. Once we have increased our capacity to process this report effectively, we will add the report back to Google Analytics. You can see link popularity statistics in other Content Optimization reports, such as the "Top Content" report or the "All Navigation" report.The turnaround was under 24 hours. That's good support. I hope the Site Overlay is back up soon - it's a killer feature.