Magento Connect is a great feature that download PEAR packages from Magento Connect marketplace and automatically install modules.
MagentoConnect creates a number of files in the downloader directory during extensions installation. Magento writes the absolute server paths in these files, so the Magento Connect downloader knows where to look to install an extension.
Sometimes after Magento store move to another server, Magento Connect downloader continue to use old server path.
To fix this issue, you need to remove file "downloader/pearlib/pear.ini".
During next extension installation, Magento Connect will update pear.ini file and server path automatically.