Posting in the Magento forums has been disabled pending the implementation of a new and improved forum solution which should better serve the community.
For new questions please post at magento.stackexchange.com, the community-run support site for the Magento community. We will be providing updates on the new forum solution soon. For questions or concerns please email firstname.lastname@example.org.
Problem with creating Magento Connect Extension (unknown channel “magento-community")
Do you have version 126.96.36.199 or 188.8.131.52-rc1? The latter requires you use “community” channel field. Download the packaging guider here for more details. http://www.magentocommerce.com/magento-connect/create_your_extension/