You may have smart quotes or smart apostrophes in your Metadata. Please see the FAQ When I try to publish a lesson to SoftChalk Cloud, I get an message "Error uploading package. Extraction failed." What should I do?
For more details on SoftChalk Cloud, please see the FAQ:
How do I get started with SoftChalk Cloud?, the SoftChalk Cloud Quick Start Guide, the SoftChalk Cloud Guide and the SoftChalk Cloud website.